The S&P 500 is one of the most popular U.S. stock indices and is often what investors and experts are referring to when they mention the "stock market." However, there's more to the market than large-cap stocks.
The lesser-known S&P 600 index is another index established by Standard & Poors that consists of 600 of the best small-cap U.S. stocks with market caps ranging from $850 million to about $3.6 billion.
