An index is a tool used to organize and categorize information in a systematic manner. In the context of books, an index is a list of the key terms or topics discussed in a book, along with the page numbers where they can be found. Similarly, in databases and search engines, an index is a system used to process and store data in a way that enables users to search and retrieve relevant information quickly and efficiently. In financial markets, an index is a measure of the performance of a group of stocks or other investments, used to track changes in the overall market.
