The S&P 500 (Standard & Poor's 500 Index) is a market-cap weighted index of 500 major U.S. companies—an essential benchmark ...

The short answer to "what is an index fund" is that it provides low-cost, broad-based exposure to the stock market. But is it the right way for you to invest?

The small-cap revival shows it has legs, and Wall Street experts say there's room for the category to keep running.