An exchange-traded fund (ETF) is a collection of securities—such as stocks—that tracks an underlying index. The best-known example is the SPDR S&P 500 ETF , which tracks the S&P 500 Index. ETFs can contain many types of investments, including stocks, commodities, bonds, or a mixture of investment types. An exchange-traded fund is a marketable security, meaning it has an associated price that allows it to be easily bought and sold.
