What Is Stock Trading? How the Stock Market Works, Explained Simply

Stock trading is the buying and selling of shares in publicly listed companies with the goal of profiting from changes in their price. This guide explains what you are actually buying, where trades happen, who is on the other side of your order, and why prices never sit still.

What a stock actually is

A stock (also called a share or an equity) is a unit of ownership in a company. If a company has issued 1,000,000 shares and you own 1,000 of them, you own 0.1% of the business. That stake gives you a claim on a proportional slice of the company's profits, a vote at shareholder meetings, and a share of whatever is left if the company is ever sold or wound up.

Companies issue shares to raise money. The first time they sell shares to the public is called an initial public offering (IPO). After the IPO, those shares change hands between investors on the secondary market, which is what people normally mean when they say "the stock market." The company itself is not involved in these later trades and does not receive the money; one owner is simply selling to another.

The price of a share is whatever the most recent buyer and seller agreed on. Multiply that price by the total number of shares and you get the company's market capitalization: the market's collective estimate of what the whole business is worth.

What stock trading means

Stock trading is buying shares with the intention of selling them later at a higher price (or, with short selling, selling first and buying back lower). The defining feature of a trader, compared with an investor, is the time horizon: traders typically hold positions for minutes to months, and their profit comes from price movement rather than from dividends or decades of compounding.

That distinction changes everything downstream: how you pick stocks, how often you look at your screen, how much you pay in transaction costs and taxes, and how much skill is required to come out ahead. We compare the two approaches in detail in Trading vs. Investing.

Where trades happen: exchanges and brokers

Shares are traded on stock exchanges, regulated marketplaces that list companies and match orders. The largest are the New York Stock Exchange (NYSE) and the Nasdaq in the United States; others include the London Stock Exchange, Euronext, the Tokyo Stock Exchange, and dozens more. Each exchange has set trading hours. US markets run from 9:30 a.m. to 4:00 p.m. Eastern Time on weekdays, with thinner "pre-market" and "after-hours" sessions on either side.

You cannot trade on an exchange directly. Instead you open an account with a broker, a licensed firm that routes your orders to the market and holds your shares and cash. In most countries brokers are regulated and your assets have some protection if the broker fails (in the US, SIPC coverage protects up to $500,000 in securities per customer, including up to $250,000 in cash). Many brokers now charge zero commission on stock trades and earn money instead from interest on cash balances, margin lending, and payments from market makers for routing orders to them.

How a trade is matched: bid, ask, and spread

At any moment there is a queue of people wanting to buy a stock and a queue wanting to sell it. The highest price a buyer is currently willing to pay is the bid; the lowest price a seller will accept is the ask (or offer). The gap between them is the bid-ask spread.

The exchange's matching engine pairs incoming orders with the best available prices on the opposite side, in price-then-time priority. Each match is a trade, and the price of the latest trade is what you see flashing on a quote screen. Our guide to stock order types explains how to control the price you actually get.

Why stock prices move

A price changes only when the balance between buyers and sellers changes. If more people want to buy at the current price than sell, buyers must raise their bids to attract sellers, and the price ticks up. The reverse pushes it down. Everything that moves a stock does so through this mechanism. The usual triggers are:

• Company news: quarterly earnings reports, guidance changes, product launches, lawsuits, executive departures, mergers and acquisitions.
• Economic data and interest rates: inflation figures, jobs reports, and central bank decisions change the value investors place on future profits.
• Sector and market sentiment: stocks tend to move together. A sell-off in technology can drag down a solid company that did nothing wrong.
• Supply and demand quirks: index rebalances, large institutional orders, options expirations, and short squeezes can push prices for reasons unrelated to the business.

Over long periods, prices track the earnings a company actually produces. Over short periods, they track expectations, positioning, and emotion. Traders live in that second world, which is why technical analysis, the study of price and volume patterns, is so popular among them.

Who is on the other side of your trade

It helps to know who you are trading against. The main participants are:

• Retail traders like you, trading their own money through online brokers.
• Institutional investors: pension funds, mutual funds, ETFs, and insurers that move very large sums and often hold for years.
• Market makers: firms that continuously quote both a bid and an ask, earning the spread in exchange for providing liquidity.
• Hedge funds and proprietary trading firms, including high-frequency traders whose algorithms react in microseconds.

Institutions account for the large majority of trading volume. This is a sobering fact for beginners: the counterparty to your trade is frequently a professional with better data, lower costs, and faster execution. Your edge as an individual is not speed. It is patience, the freedom to sit out, and the ability to take small positions in places big money cannot bother with.

Long and short: two ways to trade

Buying a stock in expectation that it rises is called going long. It is the natural starting point, and your maximum loss is what you paid.

Going short means borrowing shares from your broker, selling them, and hoping to buy them back later at a lower price before returning them. Short selling lets you profit from falling prices, but your potential loss is theoretically unlimited because there is no ceiling on how high a stock can go. It requires a margin account and is best left until you have real experience.

What it costs to trade

Costs are quieter than they used to be, but they add up, especially for active traders:

• Commissions: often zero for US stocks at major online brokers, but not everywhere and not for every product.
• Spread: paid on every round trip, as explained above.
• Slippage: the difference between the price you expected and the price you got, common in fast or thin markets.
• Margin interest: charged if you borrow from your broker to trade.
• Taxes: in many countries, including the US, profits on positions held for a year or less are taxed as ordinary income, a higher rate than long-term capital gains.
• Regulatory and exchange fees: small per-trade charges that brokers usually pass through to you.

Is stock trading right for you?

Trading is a skill, and like any skill most people are not good at it when they begin. Studies of retail traders across several countries consistently find that the majority of frequent traders underperform a simple buy-and-hold index fund, mostly because of costs and poor timing. That does not mean trading is impossible to do well. It means you should approach it as a craft to be learned with small amounts of money, a written plan, and strict risk management, rather than as a lottery ticket.

If you are still curious, the next step is our step-by-step guide to starting trading, which walks through choosing a broker, funding an account, and placing a first trade without betting the house.

Frequently asked questions

Is stock trading the same as investing in stocks?

No. Both involve buying shares, but trading aims to profit from short-term price changes over days, weeks, or months, while investing aims to benefit from a company's growth over years. Trading requires more time and more skill, and it typically costs more in fees and taxes.

How much money do you need to start trading stocks?

With fractional shares and commission-free brokers you can technically begin with a few dollars. A more realistic starting point is an amount you could lose entirely without changing your life, since your first months are for learning, not earning. In the US, placing four or more day trades within five business days in a margin account requires at least $25,000 in equity under the pattern day trader rule.

Can you lose more money than you put in?

If you buy stocks with cash only, the most you can lose is the amount you invested. Losses can exceed your deposit if you trade on margin (borrowed money) or sell short, which is why beginners should avoid both.

What is the difference between a stock and a share?

In everyday use they mean the same thing. Strictly, "stock" refers to ownership in a company in general, while a "share" is a single unit of that stock: you own 100 shares of a company's stock.

What moves stock prices the most?

In the short term, surprises: earnings results that beat or miss expectations, unexpected economic data, and sudden shifts in market sentiment. Over the long term, a company's actual earnings growth is by far the biggest driver.