Search Engines  

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Search Tools

There are two main types of search tools you can use to find information on the Internet: search engines and subject directories.

Let’s start with search engines since these are probably what you’ve used to find information.

Here are a few names you might recognize: Yahoo!, Google, Microsoft Live Search.

And a few that you might not: Hakia, GigaBlast, Cuil.

How do Search Engines Work?

A search engine doesn’t actually search “the Internet.”  Instead, a search engine is actually a giant database of websites containing information on millions or even billions of webpages. 

What is a database?

A database can be defined as "An organized collection of records presented in a standardized format" (http://www.usd.edu/library/instruction/glossary.shtml). 
At this point, most databases are computerized, but you could also think of a telephone book as a non-computerized database.  The records in a telephone book are organized alphabetically and each record contains standard pieces of information: name, address, telephone number.

Search Engine Databases

Search engines build their databases by sending out programs called spiders or crawlers that scan the web and save information about web pages into records for the websites.  Different search engine spiders scan the web and retrieve the information differently, so each search engine contains different information. Some pages are not found in search engine databases because they are too new, or not popular enough to have been discovered. Others cannot become part of the search engine's database, for a variety of reasons: for instance, they might require a password to view; they might contain instructions telling the search engine to ignore them; or the page might have been dynamically generated (for instance, created as the response to a search query).

When you enter your search in the search engine, it will display the results from its database that match your search, usually putting what it considers the most relevant results first.  Different search engines have different ways of determining relevance--another reason different search engines give you different results.

Let's look at some different search engines.

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