Web directories index a subset of the Web, broken down by categories much like a library catalog.
Usually these hand-picked sites are superior in quality to those found with a generic search engine. Like search engines, Web directories have search fields where you can type a search term or phrase. Directories are especially good if you are looking for lots of information on a single topic, or if you want to find several sites dealing with the same general subject. Web directories index only a small portion of the Web, but they do it very well. Use a search engine if you are looking for a specific word or phrase, and you don't care where you find it.