It has become a portal, or gateway, for Internet users. The first Web portals were online services, such as AOL, that provided access to the Web, but by now most of the traditional search engines have transformed themselves into Web portals to attract and keep a larger audience. Today, although there is a clear distinction between portals and search engines, you will often hear the terms used interchangeably. Key differences between search engines Just as most portals are different, so are most search engines. These differences are explained by the methods that the search engines use to assemble, index and rank their databases.
Search engines create their databases using spiders, eyeballs, or a combination of the two.
A spider is a computer program that automatically crawls across the Web, from link to link, and sends information back to the search engine for indexing and ranking. One of the first search engines to use this technology is appropriately called Webcrawler. At the other extreme, are search engines that use eyeballs to create their databases and indexes. These human eyeballs review and categorize Web sites according to specific guidelines. Most sites in it are suggested to us by users.