What is a Web directory? Although the terms search engine and subject directory are sometimes used interchangeably, they are not the same thing.

How A Web Directory Works

A Web directory organizes Web sites by subject, and is usually maintained by humans instead of software. The searcher looks at sites organized in a series of categories and menus. Web directories are usually much smaller than search engines' databases, since the sites are looked at by human eyes instead of by spiders.

There are two ways for sites to be included in a Web directory's listings; either the site owner can submit the site to the Web directory, or the directory's editor(s) will eventually come across that site.

Source: about.com