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How Does the Stock Market Work?

Updated: April 16, 2021, 4:23 p.m.

You may have heard that investing in stocks can be a great way to create wealth over time, and it's certainly true. But do you really know how the stock market works? Or what makes a stock market different from a stock exchange or stock index? Do you know what a stock is? If you're curious, here's a rundown of the basics of stock markets, stock exchanges, and stock indexes.

How does the stock market work?

Before we can get into stock markets, you need to understand stocks and how they work on a basic level.

What is a stock?

Stocks, also known as equities or publicly traded companies, represent ownership interests in businesses that choose to have their shares available to public investors. A share of stock represents an ownership interest in a company -- if you buy a share of Apple (NASDAQ:AAPL), you own a small part of the business and get to share in the company's success. In other words, instead of being owned by an individual or a private group, some companies choose to "go public," meaning that anyone can become a part owner by purchasing shares of the company's stock.

Stock market basics

So how does the stock market work? Stock markets facilitate the sale and purchase of these stocks between individual investors, institutional investors, and companies.

The vast majority of stock trades take place between investors. That means, for example, that if you want to buy shares of Microsoft (NASDAQ:MSFT) and hit the "buy" button through your broker's website, you are buying shares that another investor has decided to sell -- not from Microsoft itself. By purchasing shares of a stock, you become an investor in the underlying company.

How are prices determined on a stock market?

Stock prices on exchanges are governed by supply and demand, plain and simple. At any given time, there's a maximum price someone is willing to pay for a certain stock and a minimum price someone else is willing to sell shares of the stock for. Think of stock market trading like an auction, with some investors bidding for the stocks that other investors are willing to sell.

If there is a lot of demand for a stock, investors will buy shares quicker than sellers want to get rid of them, and the price will move higher. On the other hand, if more investors are selling a stock than buying, the market price will drop.

Taking it a step further, it's important to consider how it's possible to always buy or sell a stock you own. And that's where market makers come in.

Did You Know?

A stock's price is governed by supply and demand. If a lot of people want to own part of a certain company, then that company's stock price rises.

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Market makers ensure there are always buyers and sellers

To make sure there's always a marketplace for stocks on an exchange and investors can choose to buy and sell shares immediately whenever they want to during market hours, individuals known as market makers act as intermediaries between buyers and sellers. Here's a rundown of what investors should know about the process:

  • Market makers buy and hold shares and continually list buy and sell quotations for shares.
  • The highest offer to buy shares listed from a market maker at any given time is known as the bid, and the lowest offered selling price is known as the ask.
  • The difference between the two is called the spread.

The main reason for using the market maker system as opposed to simply letting investors buy and sell shares directly to one another is to be sure there is always a buyer to match with every seller and vice versa. If you want to sell a stock, you don't need to wait until a buyer wants your exact number of shares -- a market maker will buy them right away.

What happens when you buy a stock?

Investors must carry out the transactions of buying or selling stocks through a broker, which is simply an entity licensed to trade stocks on a stock exchange. A broker may be an actual person whom you tell what to buy and sell, or, more commonly, this can be an online broker -- say, TD Ameritrade or Fidelity -- that processes the entire transaction electronically.

When you buy a stock, here's the simplified version of how it works:

  • You tell your broker (or input electronically) what stock you want to buy and how many shares you want.
  • Your broker relays your order to the exchange, and a market maker sells you shares at the current market price.
  • The shares are then delivered to your account.
"The Market is Up!"

When someone says "the market is up" or that a stock "beat the market," they are referring to a stock index.

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How does a stock index track the stock market?

You've probably heard statements such as, "The market is up," or that a stock "beat the market." Often when discussing the stock market, people generalize "the market" to a stock index. Stock indexes, such as the S&P 500 or the Dow Jones Industrial Average, are a representation of the performance of a large group of stocks (but often not an entire stock exchange) and are used as a benchmark to compare the performance of individual stocks or an entire portfolio. For example, the S&P 500 index tracks the performance of 500 of the largest publicly traded companies in the U.S.

Indexes are a convenient way to discuss an approximation of what is happening in the market, but it's important to understand that the major stock indexes you see on TV and in the news do not fully represent the entire stock market.

Stock markets, stock exchanges, and stock indexes

There are three different terms here with similar and often misunderstood meanings. A stock market refers to the process and facilitation of investors buying and selling stocks with one another. A stock exchange is the actual intermediary that connects buyers with sellers, such as the New York Stock Exchange (NYSE). A stock index is a numerical representation of a group of stocks that is used to track their collective performance.

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