An index may refer to any of the following:
1. An index is a method of sorting data by creating keywords or a listing of the data. A great example of an index of Computer Hope's hardware listing. See our site map for a full index of the Computer Hope site.
2. When referring to the Internet or web pages, an index is a file named as index.htm, index.html, index.asp, or index.php. The index file is the first file loaded when accessing a directory on a website. For example, when visiting Computer Hope at https://www.computerhope.com you are really accessing https://www.computerhope.com/index.htm since both addresses point to the same file. Suppose the index file was missing from the directory and directory indexing is not disabled in the .htaccess file. In this case, the visitor would see all directories and files in that directory, instead of a web page or error message.
3. An index may also be a summary or section of documents created to allow another program or search engine to capture keywords or search several documents without opening multiple files.