A subject directory is a catalog of sites collected and organized by humans . Directories are also useful for finding information on a topic when you don't have a precise idea of what you need. Many large directories include a keyword search option which usually eliminates the need to work through numerous levels of topics and subtopics.
Directories cover only a small fraction of the pages available on the Web.
Most effective for finding general information on popular or scholarly subjects. If you are looking for something specific , use a search engine. Humans organize and catalog subject directories, Search engines rely on computer programs called spiders or robots to crawl the Web and log the words on each page. The search engine scans its database and returns a file with links to websites containing the word or words specified. Search engines often return thousands of results.