Search engines break down into two categories--directories and indexes. Directories, such as Yahoo!, are good at identifying general information. Like a card catalog in a library, they classify websites into similar categories, such as accounting firms, English universities and natural history museums. The results of your search will be a list of websites related to your search term. For instance, if you are looking for the Louvre museum website, use a directory.
However, if you want specific information, such as biographical information about Leonardo da Vinci? Web indexes are the way to go, because they search all the contents of a website. Indexes use software programs called spiders and robots that scour the Internet, analyzing millions of web pages and newsgroup postings and indexing all of the words.
Indexes like MSN Search and Google find individual pages of a website that match your search criteria, even if the site itself has nothing to do with what you are looking for. You can often find unexpected gems of information this way, but be prepared to wade through a lot of irrelevant information too.
Search results may be ranked in order of relevancy--the number of times your search term appears in a document--or how closely the document appears to match a concept you have entered. This is a much more thorough way to locate what you want.
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