1. Search Engine - Is a database of web sites that is ranked according to the computerized criteria that the programmers decide upon called an algorithm. Various search engines determine ranking on their own different factors of importance or relevancy. For the last few years the Google search engine was the most popular search engine supplying the search results for Yahoo and to a lesser extent MSN and AOL. This all changed recently after Yahoo purchased different search engine companies and developed its own search engine. Soon MSN will enter this market with its own search engine algorithm.

Searchers input keyword queries into search boxes and are given results from the databases of the search engines in accordance with the ranking algorithm from whatever search engine they are using.

In other words, search engines index sites it feels will be of value to its customers, which are Internet surfers searching for information.

The most important concept to grasp with a search engine, is that it uses an automated computerized system to find and rank the sites within its database of web sites.

2. Internet Directory - An Internet directory is a large listing of categorized web sites - however the concept that should be understood with the Internet directories, is that they actually have editors that decide what goes into the directory. Remember an Internet directory is decided and managed by human editors, while in contrast, a search engine is ranked by a computerized algorithm or system. Directories are important to get links from because, they will raise your rankings in the Google algorithm (which is based on PageRank