Foundationsexplainers
How Stock Markets Work: Shares, Prices, and Exchanges
Learning objectives
- Explain what a share of stock represents
- Describe how exchanges match buyers and sellers
- Explain what moves stock prices
- Distinguish primary from secondary markets
What a share is
A share is fractional ownership of a company — a claim on its future profits, paid as dividends or reflected in the share price. Limited liability means the most you can lose is your investment. When firms need capital to grow, they sell shares to the public in an IPO; after that, shares trade among investors.
A stock price reflects the market's collective forecast of future profits, discounted for risk and time.
How exchanges work
Exchanges are auction venues where buy and sell orders meet. Market makers quote continuous prices, keeping trading smooth; electronic order books match the best bid with the best ask in milliseconds. Liquidity — how easily you can trade without moving the price — is the market's lifeblood.
What moves prices
Prices move on news about earnings, interest rates, and risk appetite — but only surprises matter, since expected news is already priced in. This is the efficient-market intuition: prices reflect available information, so consistently beating the market requires either luck, private information, or genuine skill in interpreting public data.
Indexes like the S&P 500 track baskets of stocks, letting investors benchmark performance and buy the whole market at once.
Primary vs secondary markets
The IPO primary market raises new capital for firms; the secondary market — where most trading happens — just transfers ownership between investors. Secondary trading still matters: liquid markets make IPOs possible, giving firms a reason to go public in the first place.
This article explains market mechanics. It is not investment advice.
Key points
- A share = fractional ownership and a claim on future profits
- Exchanges match orders; market makers supply liquidity
- Prices reflect expected future profits, discounted for risk
- Only surprises move prices — expected news is priced in
- Secondary markets enable primary fundraising
Common misconceptions
✓ Truth: Equity is ownership, not a loan — shareholders are last in line in bankruptcy, unlike bondholders.
✓ Truth: Price per share is meaningless alone; market capitalization (price x shares) measures company value.
✓ Truth: Transaction costs, taxes, and competition make consistent short-term outperformance extremely rare.
Frequently asked questions
What is an IPO?
An initial public offering — the first sale of shares to the public, raising capital for the company.
What is a dividend?
A cash distribution of profits to shareholders; firms may instead reinvest, lifting the share price.
What causes a market crash?
Usually a repricing of expectations — about earnings, rates, or risk — amplified by leverage and panic selling.
What is diversification?
Spreading investments so no single company's fate decides your outcome; the one free lunch in finance.