Stocks Explained

A stock isn't a lottery ticket, a line on a chart, or a Reddit meme. A stock is a legal claim on the future cash flows of a specific business, sliced into a tradeable unit. Everything else - price movements, charts, news, even your account balance - is downstream of that one fact. This lesson is the full picture: what stocks actually represent, the seven flavors every trader should recognize, how market capitalization works, the math behind P/E ratio and EPS, how stock splits and short sellingShort sellingBorrowing shares to sell, with the intent to buy them back lower. Profits when price falls. Losses theoretically unlimited as price rises.Read in glossary → mechanically work, and how the NYSE differs from the NASDAQ in ways that affect the instrument you're actually trading.

What are stocks?

A stock (also called an equity or a share) is a unit of ownership in a corporation. Own one share of Apple, and you legally own one 15-billionth of the company's assets, earnings, and voting power. You benefit proportionally if Apple makes money; you lose proportionally if it doesn't.

When a company "goes public" via an IPO (initial public offering), it issues a fixed number of shares and sells some of them to raise cash. Those shares then change hands between investors on stock exchanges. The company doesn't make money on secondary trades - only the people who held shares before the sale do.

Two details matter here that most beginner lessons skip:

• Shares outstanding is the total number of shares the company has issued. Float is the subset of those shares that are actually tradeable on the open market (excludes insider holdings, institutional lock-ups, etc.). A stock with 1B outstanding but only 100M float behaves very differently from one with 1B of each.
• Share classes. Many companies issue multiple classes with different voting rights. Google has GOOGL (Class A, voting) and GOOG (Class C, non-voting); the prices are nearly identical but not the same instrument.

Common stock vs preferred stock

The two major types of stock answer different trade-offs.

Unless a lesson specifically says "preferred," assume every discussion of "stocks" means common stock.

The seven types of stocks every trader should recognize

These aren't mutually exclusive - Apple is simultaneously a mega-cap, a blue chip, and (by some definitions) a growth stock. But each category tells you something different about what to expect from the instrument.

One stock can change categories over time. Amazon was a growth stock for 25 years; most analysts now consider it a blue-chip growth hybrid. The categories are useful because they tell you what kind of volatility to expect - and what kind of thesis is supposed to move the price.

What is market capitalization? - and why "large cap vs small cap" matters

Market capitalization (or "market cap") is the total dollar value of all outstanding shares of a company. It's the most common way to measure how big a company is.

Market cap = Share price × Shares outstanding

A $500 stock with 100M shares outstanding is a $50B company. A $5 stock with 10B shares outstanding is also a $50B company. Share price alone tells you nothing about company size. That's a common beginner mistake - assuming a $5 stock is "cheaper" than a $500 stock. It isn't; it's just smaller-denominated.

Market cap tiers - the practical differences

Same-price illusion. If you see a stock at $220/share, that gives you zero information about the company. Apple at $220 is a ~$3T company; a small-cap at $220 might be a $500M company with a fraction of the float. The trading experience - spreads, slippage, gapGapA discontinuity on the chart - the open of one bar is meaningfully above or below the close of the prior bar.Read in glossary → risk - is completely different.

How are stocks valued? - the fundamentals that actually matter

Fundamentals answer the question: what should this stock cost, roughly? The five most important metrics:

Earnings per share (EPS)

EPS = Net income ÷ Shares outstanding

Net income is total profit after taxes and expenses. Divide by shares outstanding to get per-share profit. Rising EPS over time is the core signal of fundamental strength.

If a company earns $10B in net income with 2B shares outstanding, EPS = $5. Trailing EPS uses the last 12 months; forward EPS uses analyst estimates for the next 12 months.

P/E ratio (price-to-earnings)

P/E = Share price ÷ EPS

The single most-quoted valuation shorthand. Roughly 'how many years of current earnings am I paying for?' S&P 500 historical median: ~15-17. Above 25 = priced for growth; below 10 = priced for problems.

P/E by sector varies wildly. Tech trades at 25-35× on average. Utilities trade at 15-20×. Banks trade at 10-14×. Comparing Apple's P/E to JPMorgan's P/E without adjusting for sector is a beginner mistake.

Dividend yield

Dividend yield = (Annual dividend ÷ Share price) × 100

The annualized dividend as a percentage of current share price. A 4% yield means you'd earn $4 per year on every $100 invested, before any capital appreciation.

A 2.5% yield on a steady large-cap is normal. A 10%+ yield is a red flagFlagA brief consolidation (the flag) after a sharp move (the flagpole). Classic continuation pattern.Read in glossary → - usually the company just dropped 40% on bad news and the yield math hasn't caught up yet. Very high yields often reflect distress, not generosity.

PEG ratio (growth-adjusted P/E)

PEG = P/E ÷ Earnings growth rate (%)

Adjusts P/E for earnings growth rate (%). PEG = 1 is fairly valued; <1 may be undervalued; >1 may be expensive relative to growth.

A stock with a P/E of 30 sounds expensive. But if it's growing earnings 30% per year, PEG = 1.0 - reasonably priced for the growth. PEG corrects for one of the most common fundamental-analysis mistakes: confusing high P/E with "overvalued."

Debt-to-equity ratio

D/E = Total debt ÷ Shareholders' equity

Measures how much leverage the company is running. Below 1.0 is conservative; 1.0-2.0 is normal; above 2.0 needs scrutiny; above 3.0 in a rising-rate environment is a warning sign.

Stock splits and reverse splits - mechanics and math

A stock split is when a company increases the number of shares outstanding and proportionally decreases the price per share. It changes the wrapper, not the underlying business.

Example: a 4-for-1 split. Before: 1,000,000,000 shares × $400 = $400B market cap. After: 4,000,000,000 shares × $100 = same $400B market cap.

Why companies do it:

• Lower per-share prices feel more accessible to retail investors (psychology, not math).
• Keeps the stock price in a "typical" range (historically, companies split when shares drift too high; less important now with fractional shares widely available).
• Doesn't create or destroy value - if you owned 10 shares at $400 before the split, you now own 40 shares at $100 after. Same $4,000.

Reverse splits - the distress signal

A reverse stock split is the opposite: the company consolidates shares, increasing per-share price.

Example: a 1-for-10 reverse split. Before: 1,000,000,000 shares × $0.50 = $500M market cap. After: 100,000,000 shares × $5.00 = same $500M market cap.

Reverse splits are almost always defensive - companies use them to:

• Meet exchange minimum-price listing requirements (NYSE: $1; NASDAQ: $1; failure to maintain triggers a delisting warning).
• Escape penny-stock status and the stigma that comes with it.
• Look "cheaper" on a per-share basis without changing fundamentals.

Historically, a reverse split is a bearish signal - the companies announcing them tend to underperform afterward because the underlying business problems remain. The split doesn't fix anything; it resets the optics.

How to make money on stocks - going long vs selling short

Stocks go up. Stocks also go down. Traders can profit from either direction - but the two positions are not mirror images.

Going long - the standard approach

Buy at a lower price, sell at a higher price. Classic. Your maximum loss is capped at your entry (the stock can only go to zero), and your maximum gain is theoretically unlimited.

Short selling - borrowing shares to sell high, buying low to return

Short selling is profiting from a stock going down. The mechanic:

1. You borrow shares from your broker (who borrows them from another account).
2. You immediately sell them at the current market price.
3. Sometime later, you buy them back (ideally at a lower price).
4. You return the shares to the lender; you keep the difference.

Requirements:

• MarginMarginBorrowed capital used to increase position size. Amplifies both gains and losses proportionally.Read in glossary → account (a cash account cannot short - no borrowing allowed).
• Locate feeLocate feeA fee charged by your broker when you short a hard-to-borrow stock. The broker has to find shares to lend you, and that cost gets passed through. Can range from a fraction of a cent up to 100%+ annualized for very-hard-to-borrow names. Often quoted as a daily rate.Read in glossary → for shares that are hard to borrow.
• Daily interest (borrow rate) while the position is open - ranges from 0.25%/year on easy-to-borrow names to 100%+/year annualized on hard-to-borrowHard-to-borrowA stock with limited share supply available for short-selling. Borrowing it incurs a locate fee that can dwarf any directional gain. Common for low-float names, recent IPOs, or short-squeeze candidates. Always check HTB status BEFORE shorting - the fee can turn a winning trade into a loser.Read in glossary → ones.

Worked example · a short trade, step by step

You think XYZ at $100 is overvalued and will drop.

Monday: Borrow 100 shares, sell them at $100 = +$10,000 cash in your account. But you now owe 100 shares back to the lender, and the current market value of that obligation is $10,000. Net: $0 P&L.

Friday: XYZ drops to $80. You buy 100 shares in the market for $8,000, return them to the lender. You keep $2,000.

Gross profit: $2,000. Minus: 5 days of borrow interest, say $15. And any locate fees if it was hard-to-borrow. Net: ~$1,985.

If instead XYZ had rallied to $130 and you were forced to close: you'd buy 100 shares at $13,000, return them, lose $3,000 - a 30% loss on a 30% move against you, same as a long position. Unless the stock kept running. Unless it 5×'d. The long position caps at -100%; the short position doesn't cap.

ETB vs HTB - easy vs hard to borrow

Not every stock is equally shortable. Easy-to-borrow (ETB) stocks have abundant available share supply - most large-caps qualify. Hard-to-borrow (HTB) stocks have limited available supply; borrow rates can be astronomical, and locates may run out mid-day.

Signs a stock is HTB (and the short side is crowded):

• Borrow rates above 10% annualized.
• Short interest as % of float above 15%.
• Low float (<50M shares).
• Recent retail-driven pump.

Short squeezes - when the short side gets trapped

A short squeeze happens when a stock with heavy short interest starts rallying. Shorts are forced to buy to cover their positions, which pushes the price higher, which forces more shorts to cover, and so on - a self-reinforcing loop.

The 2021 GameStop episode was the modern reference: GME ran from $20 to $480 in two weeks, with short interest briefly exceeding 140% of float (because of re-borrowing of the same shares). Funds that had shorted it at $20 faced margin calls at $200 and had to buy at any price.

Short-squeeze warning signs:

• Short interest > 20% of float.
• Retail momentum + rising volume.
• Price above all major moving averages despite "bearish fundamentals."

Where stocks trade - exchanges, tickers, and listing mechanics

Stocks don't just "exist" - they exist on specific exchanges under specific rules.

NYSE vs NASDAQ - what's actually different

The two major US exchanges are not interchangeable.

Some key facts most guides miss:

• A stock is listed on one exchange but can trade on many (via Alternative Trading Systems and dark pools). 30-40% of US equity volume now trades off-exchange.
• NYSE-listed stocks usually have 1-4 character tickers (F, GE, BAC, XOM, WMT). NASDAQ-listed stocks usually have 4-5 character tickers (AAPL, MSFT, GOOGL, NFLX, COIN). Not a hard rule, but close to one.
• OTC (over-the-counter) stocks trade between dealers without a central exchange. OTC Pink / Pink Sheets is the lowest-regulated tier - most penny stocks live here and should be approached with extreme caution.

Market hours for US stocks

The volume smile from the Market Foundation lesson tells the fuller story - peak volume (and tightest spreads) cluster at the open and close of the regular session.

Common questions about stocks

What's the difference between common and preferred stock? Common stock gives you voting rights and variable dividends (if any), with unlimited upside. Preferred stock gives you a fixed dividend and priority in bankruptcy but usually no voting rights and limited upside. Most traders trade common; preferred is mostly for income-focused investors.

How do I calculate market cap? Market cap = current share price × total shares outstanding. You can find shares outstanding on any financial data site (Yahoo Finance, Google Finance, the company's investor relations page).

Are large-cap stocks safer than small-cap stocks? Generally yes, on average. Large-caps have more diversified revenue, deeper analyst coverage, more stable price action, and tighter spreads. Small-caps can deliver bigger returns but with proportionally bigger drawdowns and gap risk. "Safer" ≠ "bulletproof" - large-caps fall in bear markets too.

What's the difference between a stock split and a reverse stock split? A stock split increases the share count and decreases the price per share (e.g., 2-for-1 doubles shares, halves price). A reverse split does the opposite and is usually defensive - companies use it to avoid delisting when the stock price falls too low.

Can I lose more than my investment when short selling? Yes. Because a stock's upside is theoretically unlimited, a short position's downside is too. If you short at $100 and the stock runs to $400 before you can cover, you've lost $300/share on a position that originally earned you only $100/share. Long positions cap at -100%; short positions don't cap.

How is a P/E ratio of 30 different from 15? A P/E of 30 means you're paying $30 for every $1 of current annual earnings - more expensive on that measure than a P/E of 15. But "expensive" is context-dependent: a fast-growing company may deserve a 30 P/E because its earnings will double in a few years. Always compare P/E to the stock's sector average and growth rate.

What are blue-chip stocks? Large, financially stable, well-established companies with long operating histories and strong brand recognition. Apple, Microsoft, Johnson & Johnson, Coca-Cola, McDonald's. They trade with lower volatility and tighter spreads than the broader market and are considered "core" holdings for most long-term portfolios.

Math cheatsheet

Market cap = Share price × Shares outstanding

EPS = Net income ÷ Shares outstanding

P/E = Share price ÷ EPS

Dividend yield = (Annual dividend ÷ Share price) × 100

PEG = P/E ÷ Earnings growth rate (%)

D/E = Total debt ÷ Shareholders' equity

Key takeaways

• A stock is a legal ownership unit in a company. Share price alone tells you nothing about company size - you need market cap for that.
• Common stock (with voting rights, variable dividends, unlimited upside) is what 99% of traders actually trade. Preferred stock is an income-focused hybrid.
• Seven major stock categories overlap - a company can be a blue-chip, a mega-cap, and a dividend stock all at once. The categories tell you what kind of volatility and thesis to expect.
• Market cap tiers span five orders of magnitude. Don't treat a small-cap like a mega-cap - they don't trade the same way.
• P/E ratio is the most quoted fundamentals metric, but always compare within sector and adjust for growth (PEG).
• A stock split changes the wrapper, not the business. A reverse split is almost always a distress signal.
• Short selling profits from falling prices but has asymmetric risk - there's no cap on how much you can lose.
• NYSE and NASDAQ aren't interchangeable. NYSE hosts traditional industries with stricter listing rules; NASDAQ hosts tech with faster electronic execution.
• The strongest signal of a real business is growing EPS over time, not a rising share price. The two eventually align.

Up next: bonds, ETFs, options, and the other instruments that live alongside stocks - what they are, when they're useful, and how they relate to the stock you've just learned.