Search Engines Explained

From its inception the Internet has posed to its users the problem of how to get the information they need from a large network of interconnected computers. If you know which particular Web site has your information and you know its URL (see the definitions section of "What Technologies?" for a definition of "URL), it is simply a matter of typing it into the address bar at the top of your Web browser. But much, if not most, of the time you will be looking for specific information without knowing which particular Web site has that information. In such cases even a huge directory listing every Web site that currently exists would be of little use. So how do you find the Web site you really want on a World Wide Web that contains millions upon millions of sites?

You use a search engine.

Select a question below to learn more about search engines.

1. What is a search engine and how does one work?
   
2. What are some popular search engines?
   
3. Are there any search engines designed for kids?
   
4. Do search engines index the entire Internet?
   
5. What are Boolean operators?
   

What is a search engine and how does one work?

It is easiest to think of a search engine as a Web site that scours the World Wide Web looking for other sites that are in some way related to the search terms that you specify. Although that is the easiest explanation, it is also a bit inaccurate. Actually, a search engine runs programs (called "spiders") that continuously explore the World Wide Web and index the information on the Web sites that they encounter along the way. This index forms a huge database of Web site addresses that are associated with different key words that have been found on the Web sites themselves. When you use a search engine, it is this database that is searched and not the Internet itself. The search results are links to previously indexed sites on the World Wide Web. That is why search engines sometimes produce "dead links"—that is, links to Web sites that no longer exist.

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