What is a web index?
In Summary:
A web index collects and organizes resources that are available via the World Wide Web, and is designed to provide a starting point for locating information. Web indexes may be organized in a variety of ways, including alphabetically and topically, and generally offer users the option of connecting directly to the resources listed.
Web indexes are not a comprehensive repository of all the information available,
although they can list thousands of resources. Search options are sometimes provided at
the index site to assist users with locating resources within the index.