<human>: What's the difference between an ETF and a mutual fund?
<bot>: An ETF is a type of investment that tracks an index, such as the S&P 500 or the Dow Jones Industrial Average. Mutual funds are similar to ETFs, but they are managed by professional money managers who invest in a variety of securities. ETFs tend to have lower fees than mutual funds, which can make them more cost-effective for investors.