Index Fund
An index fund is a mutual fund or ETF that holds every stock or bond in a market index, such as the S&P 500, instead of trying to pick winners. Because there is no active manager, fees are very low and returns match the market. Index funds are the backbone of most long-term investing plans.
Example
An S&P 500 index fund with a 0.03% expense ratio costs just $3 per year on a $10,000 investment.