Indexes are tools used to organize and summarize information, making it easier to locate specific data within a larger set. In the context of books, an index is typically found at the end and lists topics, names, or terms alphabetically along with their corresponding page numbers. This helps readers quickly find the information they need without having to read through the entire text. In finance, an index refers to a statistical measure that represents the performance of a group of assets, such as stocks or bonds. For example, the S&P 500 index tracks the performance of 500 large companies in the United States, providing investors with a benchmark to assess market trends and investment performance.