Final answer:
The S&P 500 is a broad stock index that includes many of the largest and best-known United States corporations. It provides a measure of how the overall stock market is performing.
Step-by-step explanation:
The S&P 500 is a broad stock index that includes many of the largest and best-known United States corporations. It is a weighted average market capitalization of the 500 largest U.S. companies. This index tracks the performance of the stock market as a whole, providing a measure of how the overall market is performing.