One thing that is so basic that it often still needs to clarified is the concept that a search engine and a search directory (article directory) are not the same thing. The traditional search engines add Web site pages to their databases automatically and then rank them in popularity in their search engine rankings based on user submissions. However, these search engines also periodically send their automatic robots or "spiders" out to "crawl" for new and updated information on websites that can also be indexed and added to the search engine rankings. Complex algorithms (that are comparable to the mysterious complex FICO Scores that are used to calculate your credit rating) calculate your web page's popularity on a number of different factor. The most famous example of a pure search engine like this is Google

Directories also qualify as a search site but they are not the same as a search engine. To get listed on a directory, you must actually submit your front page URL on the directory's submission form. Also instead of being evaluated by an algorithm, these pages are directly assessed by a human being. This means that your site is ranked according to the information that you submitted on your application. This is very different from a typical search engine that assesses your web ranking according to what is actually on the home page of your web site. The Open Directory, Yahoo and LookSmart are the main Internet directories that are managed in this way.

To make things even more difficult the search sites and the search engines work in cahoots together to boost each other's rankings. Almost all of the major search engines also work in tandem with a directory which is why, for instance, a listing in DMOZ almost automatically guarantees you a place on Google.
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