Definition - Web Directories

Basically, a web directory is a big list of websites organize by category.

Directories differ from search engines in that directories are human-edited. That is to say, directory editors actually review websites for legitimacy and relevancy before adding them to the directory. Search engines, on the other hand, add websites to their databases automatically and without human intervention.

How Do Directories Affect SEO?
Directories are a good way to get those all-important inbound links to your website. When you website gets listed in an older, well-established and high-ranking directory, you've just earned a link from that site. Remember, when it comes to link popularity, links from high-ranking websites relevant to your own website contribute the most to your search engine ranking.

Not All Directories Are Created Equal
It's also important to note that directories range from excellent investment to waste of time — just like any other type of website. I point this out because most directories charge a small fee for reviewing your site before inclusion. Obviously, you don't want to waste your time and money on a directory that offers little value, so it's important to screen them first.