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. Use the search tips at the bottom of this page for best results. Search engines will give you many more irrelevant and potentially undesirable hits than Web directories. This can be good and bad. Meta sites search multiple search engine and Web directory sites all at the same time, increasing your chances of finding an obscure term or phrase.