The stock market is a network of marketplaces where shares of public companies are bought and sold. Each share represents part ownership of a company and, when paired with other investments, can be used to create portfolios that grow in value over time. A share’s value is influenced by a variety of factors, including economic growth and the success or failure of individual companies. Many investors choose stocks, ETFs and mutual funds based on research and advice from financial professionals. Historically, it was common for people to work with financial advisors to execute trades, but today it is possible for individuals to open trading accounts online and invest on their own.

The modern stock market brings together buyers and sellers through a series of marketplaces called exchanges, such as the New York Stock Exchange and Nasdaq. Investors looking to buy a stock match up with sellers through brokers, who facilitate the transaction almost instantly. A stock’s price rises when there is strong demand for it, enticed by things like better-than-expected profits or a growing economy here or abroad. Similarly, a stock’s price falls when there is little demand or if current shareholders want to cash out.

A stock’s price is also affected by the movement of major market indices, which track the weighted average of the value of a group of stocks. Investors often reference a specific index, such as the Dow Jones Industrial Average or the S&P 500, to see how the overall market is performing.