How Stock Markets Work: Buyers, Sellers, and Prices in Real Time

What a Share Actually Is

When a company sells shares to the public, it divides ownership of the business into millions of equal pieces. Buying one share makes you a part-owner with a proportional claim on everything the company is worth after its debts are paid. You do not own a particular asset like a server or a building; you own a percentage of the entire enterprise. If the company distributes profits as dividends, shareholders receive a cut proportional to how many shares they hold. If the company is acquired or wound down, shareholders receive what remains after all creditors have been paid in full.

Where Trading Happens: Exchanges and OTC Markets

Most shares trade on organized exchanges. The New York Stock Exchange and Nasdaq are the two largest in the United States. An exchange provides a central, regulated venue where buyers and sellers submit orders that are matched by electronic systems. Companies must meet listing requirements — minimum size, financial disclosure obligations, governance standards — to trade on a major exchange.

Not every security trades on an exchange. Over-the-counter (OTC) markets are decentralized dealer networks where prices are quoted directly between parties. Bonds, foreign currencies, and smaller stocks that fail exchange listing requirements trade OTC, typically with less transparency and wider transaction costs.

The Bid-Ask Spread

At any moment, a traded stock has two prices:

• Bid price — the highest price any current buyer is willing to pay
• Ask price — the lowest price any current seller will accept

A trade executes when a buyer agrees to pay the ask or a seller agrees to accept the bid. The gap between the two is the spread. Liquid, actively traded stocks have spreads of fractions of a cent. Thinly traded stocks have wider spreads, which represent a real cost paid by anyone entering or exiting a position.

Types of Orders

Investors use different order types depending on their urgency and how much price control they need:

• Market order — execute immediately at the best available price; execution is guaranteed, but the exact price is not
• Limit order — set a maximum price to buy or a minimum price to sell; the order sits in the queue and fills only if the market reaches your level
• Stop order — becomes a market order once a specified trigger price is reached; often used to cap losses on an existing position

How Price Is Set by Matching Orders

There is no committee deciding what a stock should cost. The price at any moment is the last price at which a willing buyer and a willing seller agreed to transact. Exchange systems maintain a live order book — a ranked list of all outstanding buy and sell orders. Incoming orders either match existing orders immediately or join the queue. When buyers outnumber sellers at the current price, the price rises until sellers emerge. When sellers outnumber buyers, the price falls until buyers step in.

Types of Market Participants

Different actors bring different goals and time horizons to the same market:

• Retail investors — individuals buying shares for long-term goals such as retirement or wealth building
• Institutional investors — pension funds, mutual funds, and insurance companies managing large pools of capital on behalf of others
• Market makers — firms that continuously quote both buy and sell prices, earning the spread in exchange for providing the liquidity that keeps markets functional
• Algorithmic and high-frequency traders — programs executing thousands of trades per second to exploit tiny, short-lived price discrepancies

Index Funds vs. Individual Stocks

An index fund holds every stock in a benchmark — the S&P 500, for example, tracks 500 large U.S. companies weighted by market value. Rather than betting on specific winners, the investor simply captures whatever return the broad market delivers, at very low cost. Decades of research show that the majority of actively managed funds fail to outperform their benchmark index over long periods once fees are deducted. That evidence is the foundation of the case for passive, index-based investing.

Why Markets Move on Expectations, Not Just Facts

Stock prices reflect the discounted present value of what investors collectively expect a company to earn in the future. This is why a company can report record profits and still see its share price fall: if investors expected even stronger results, the actual report is a disappointment relative to what was already priced in. Conversely, a company posting a smaller-than-expected loss can see its stock rise. News moves prices only to the extent it differs from what the market had already anticipated.