The stock market is a network of exchanges where people buy and sell small ownership stakes in publicly traded companies. When you buy a share of stock, you own a tiny piece of that company, including a proportional claim on its future profits. The market serves two core purposes: it helps companies raise money to grow, and it gives everyday people a way to build wealth over time.
How Companies Enter the Market
A company starts as privately owned, meaning its shares aren’t available to the general public. When it decides to “go public,” it sells shares for the first time through an initial public offering, or IPO. This happens on what’s called the primary market. The company works with an investment bank to set a price, and investors buy those newly created shares. The money from that sale goes directly to the company, which can use it to hire, build products, expand into new markets, or pay down debt.
Once the IPO is complete, those shares move to the secondary market, which is the stock market most people picture: exchanges like the New York Stock Exchange and Nasdaq. From that point on, shares trade between individual and institutional investors. The company doesn’t receive money from these trades. Instead, buyers and sellers negotiate prices with each other, and the price of a share moves up or down based on how much demand there is for it.
What Moves Stock Prices
A stock’s price reflects what buyers are willing to pay and what sellers are willing to accept at any given moment. That balance shifts constantly based on a mix of factors. A company’s earnings reports, new product launches, or leadership changes can push its stock up or down. Broader forces matter too: interest rate decisions, inflation, employment data, and geopolitical events all ripple through the market.
At the most basic level, if more people want to buy a stock than sell it, the price rises. If more people want to sell than buy, the price falls. This can happen gradually over weeks or violently within a single trading day. Short-term price swings are common and don’t necessarily reflect a change in the company’s actual value. Over longer periods, though, stock prices tend to track a company’s real financial performance.
How the Market Is Measured
You’ll frequently hear about “the market” going up or down. That usually refers to one of three major indexes, each of which tracks a specific group of stocks to represent the broader market’s health.
- S&P 500: Tracks roughly 500 large and mid-cap U.S. companies across industries like technology, healthcare, financials, and consumer goods. Together, these companies represent about 80% of the total U.S. stock market’s value. It’s weighted by market capitalization, meaning bigger companies like Apple and Microsoft have more influence on the index’s movement than smaller ones.
- Dow Jones Industrial Average: A much narrower index of just 30 blue-chip companies chosen for their stability and industry leadership. Unlike the S&P 500, the Dow is price-weighted, so stocks with higher share prices have more influence regardless of the company’s total size.
- Nasdaq Composite: Includes over 3,000 companies and leans heavily toward technology, biotech, and fintech. It’s also market-cap weighted, which means a handful of tech giants drive much of its performance.
When a news anchor says “the market dropped 2% today,” they’re typically referring to one of these indexes, not every single stock. Different indexes can move in different directions on the same day, depending on which sectors are gaining or losing.
How People Make Money in Stocks
There are two main ways investors profit. The first is capital appreciation: you buy a stock at one price and sell it later at a higher price. If you purchase shares at $50 and sell at $75, your gain is $25 per share, minus any fees or taxes.
The second is dividends. Some companies distribute a portion of their profits to shareholders, usually quarterly. Not all companies pay dividends. Fast-growing tech firms often reinvest all their profits back into the business, while more established companies in sectors like utilities or consumer goods tend to pay regular dividends. You can spend that dividend income or reinvest it to buy more shares.
Over the long run, the S&P 500 has delivered average annual returns of roughly 10% before adjusting for inflation, based on data going back to 1928 tracked by NYU Stern. That figure includes both price gains and dividends. In any given year, though, returns can swing wildly. The market has delivered years with gains above 30% and years with losses beyond 30%. The long-term average only materializes if you stay invested through both the good years and the bad ones.
Risk and Volatility
Stocks carry real risk. Unlike a savings account, there’s no guarantee you’ll get your money back. A single company can lose most or all of its value if it runs into financial trouble, faces a scandal, or gets outcompeted. Even the broad market can decline sharply during recessions or crises, sometimes taking years to recover.
Volatility, the degree to which prices swing up and down in the short term, is the trade-off for higher potential returns. Safer investments like Treasury bills offer lower returns precisely because they carry less risk. Historically, stocks have outperformed bonds, savings accounts, and most other asset classes over periods of 20 years or more, but that comes with the understanding that any single year could be painful.
One of the most effective ways to manage risk is diversification: spreading your money across many companies and sectors so that one bad stock doesn’t sink your entire portfolio. This is where index funds and exchange-traded funds (ETFs) come in. An ETF that tracks the S&P 500, for example, gives you exposure to 500 companies in a single purchase, which means your results reflect the broad market rather than the fate of any one business.
How to Access the Market Today
Buying stocks used to require calling a broker and paying hefty commissions. Today, most major brokerage platforms let you trade stocks and ETFs with zero commission. You open an account online, link your bank, deposit funds, and start placing orders, often within the same day.
One barrier that’s largely disappeared is the cost of individual shares. Many brokers now offer fractional shares, letting you invest as little as $5 or $10 into a stock that might trade for hundreds of dollars per share. Charles Schwab, for instance, lets you buy fractional shares of S&P 500 stocks for as little as $5 each. Other platforms offer fractional shares of individual stocks and ETFs with no trade commission. Vanguard offers fractional shares of ETFs specifically. This means you don’t need thousands of dollars to start building a diversified portfolio.
Most beginners start with a brokerage account or a tax-advantaged retirement account like an IRA. The mechanics of buying are the same in both. The difference is that retirement accounts offer tax benefits for money you plan to leave invested for the long term.
Market Hours and Order Types
U.S. stock exchanges are open for regular trading from 9:30 a.m. to 4:00 p.m. Eastern Time, Monday through Friday, excluding market holidays. Some brokers also offer extended-hours trading before the open and after the close, though liquidity is thinner and prices can be more volatile during those sessions.
When you place a trade, you’ll choose an order type. A market order buys or sells immediately at the best available price. A limit order lets you set the maximum price you’re willing to pay (or the minimum you’re willing to accept when selling), and the trade only executes if the market reaches that price. For most casual investors buying well-known stocks, market orders work fine. Limit orders are useful when you want more control, especially with less frequently traded stocks where prices can jump between the time you place your order and when it fills.