Search engine optimization (SEO) is a process of raising a site`s ranking in the various search engine.This usually involves creating links from other sites,targeting keywords and building traffic.

Search Engines are index web pages based on content. Each engine works differently. They base the search results on Meta Tags, page content, title, or a combination of these. They get their content from spider programs.

Directories categorize the WWW based on input submitted by a human being.
An example is Yahoo. When someone searches for a keyword, this is referenced against a database of sites that contain a title and description for a particular site.

Most search engines include a categorized directory or guide to Web sites as part of its portal-building efforts. It is an effort to capture traffic lost to Yahoo!, which lists only sites that they feel offer valuable information.

For maximum advantage, submit your site to the directory portion of the portal. The directories and guides are becoming a major portion of the traffic generated by the search engines - separate submission required.