The people who maintain directories usually take submissions or use automated tools to find new pages on the Web. The pages are then summarized and placed into a category. In many ways, directories are organized like a library catalog with subject headings and sub-headings. Some directories will also review and rate the pages they catalog. To use a directory, you browse through the subject headings to find what you're looking for.
Many directories also make it possible to search the database by keywords.
Created in 1994, it is one of the oldest and most popular directories on the Web. Indexes Another category of search tools are indexes. The main characteristic that distinguishes indexes from directories is how their database information is gathered and organized. An index is generated automatically by using small computer programs called robots, spiders, or crawlers. These programs continuously visit web pages, record information they find, and add it to the database.