A search engine is a system that enables users to search and retrieve information from the web. Usually, search engines use a software program, generally referred to as crawlers, to index web pages. Various search engines use complex algorithms to index and categorize the web pages.
Web directories contain a collection of web pages organized into categories and sub-categories. The main difference between directories and search engine is that search engines use software to automatically index the web pages; whereas in a directory, web sites are organized into categories by people.
Why should you submit in directories?
Directories can broadly be classified into "Free Directories" and "Paid Directories". There are many free directories available on the web, such as DMOZ, Yahoo!, World Wide Index, AbiLogic, Gimpsy, JoeAnt, etc. Usually the free directories take a long time to list a submitted web site. So be patient and constantly check these directories for your site. The paid directories list a submitted site usually within a day! If you go for the paid option, you should consider the following directories: Arielis, BOTW, BlueFind, Microsoft bCentral, and GoGuides.