All website owners and website developers recognize the importance of search engine optimization. Thus, they conducted studies on how search engines come up with their lists. From one point of view, human-powered directories are easier to deal with, since what is primarily needed is excellent and informative content. For crawler-based search engines, the specific method of ranking cannot be revealed.

The directory is a type of search engine which list is not automatically assembled by electronic minions. The directory is human-powered. That is, a qualified professional reviews a submitted website and based on the quality of the site, this professional, called the editor, will determine whether he will accept or reject the website.