The stock market works through a variety of exchanges, such as the New York Stock Exchange (NYSE) and Nasdaq Stock Market (Nasdaq) in the United States. In the past, these exchanges were physical locations, but today the stock market works electronically. Companies list shares of their stock in an exchange through a process called an initial public offering (IPO), and investors can purchase or sell those shares once they are available on the market.
The stock market exchange tracks the supply and demand for each stock as well as its value. Indexes representing all or a subset of the stocks listed on an exchange or exchanges are often quoted by the press. Some of the best known of these indexes are the Dow Jones Industrial Average, the S&P 500, and the NASDAQ 100.