A fund that tracks a market index instead of trying to beat it.
An index fund holds the same securities as a market index, such as the S&P 500, aiming to match the market's return at very low cost rather than picking winners. Because it requires little active management, fees are minimal, and decades of evidence show low-cost index funds outperform most actively managed funds over the long run.
A single S&P 500 index fund gives you a slice of 500 large U.S. companies in one purchase.