The S&P 500 Index is a stock Index of 500 publicly traded companies in the United States. The stock index is created and maintained by Standard & Poor's.All companies covered by the S&P 500 are listed on major U.S. exchanges, such as the New York Stock Exchange and Nasdaq. The S&P 500 contains more companies than the Dow, so risk is more diversified and reflects broader market changes.Top 10 S&P 500 holdings: Apple, Microsoft, Amazon, Facebook, ExxonMobil, Johnson & Johnson, Berkshire Hathaway, JPMORGAN Chase, ALPHABET INC A, ALPHABET INC C (Parent company of Google) Are these companies familiar? Most of them are fortune 500 companies. So by investing in the S&P 500, you're indirectly owning these great companies.The stocks that make up the S&P 500 inde