Basically, directories are created manually, with human beings categorizing and/or ranking submitted resources. Search engines work as programmed, mechanical spiders or crawlers, visiting web sites, then creating searchable topic catalogs. A web directory is like a table of contents, filtering and organizing information for you. A search engine is more spontaneous, responding to keywords supplied by users.

Technically, Magellan and Yahoo are directories, not engines. What confuses the difference between engines and directories is that Magellan and Yahoo, for example, allow you to search their respected directories. Recently, some of the more popular search engines have added directories to their capabilities, further blurring any clear distinctions.

The best use of directories are for browsing broad subject categories such as sports, government, libraries, etc. Use search engines for more specific searches of the entire World Wide Web by submitting keywords. Some users appreciate the ease and speed of organized directories; while others with more exacting needs enter specific keywords into the search engine immediately.