What is an index fund and how do I invest in one?

An index fund is a type of investment fund that tracks a market index, like the S&P 500, by holding the same stocks in the same proportions as that index. Instead of a manager actively picking stocks, it passively mirrors the index, which keeps costs low and typically delivers returns that match the broader market. To invest in one, open a brokerage account with a provider like Fidelity, Vanguard, or Schwab, or use your employer's 401(k) if it offers index fund options. Search for a fund tracking an index you want, such as VOO or FXAIX for the S&P 500, then buy shares with however much you want to invest. Many funds have no minimum investment requirement today.