The search engines are like very large information centers, they are designed to help people find information stored on the internet. There are different ways the various search engines work but they all perform three basic tasks:
• They search the Internet - or select pieces of the Internet - based on what we call search terms,
• They keep an index of search terms, and where they can be found.
• They allow users to look for search terms found in their index.
The Early Search Engines had an index of a few hundred thousand pages and documents, and received only about one to two thousand searches per day.
The Search Engine of today indexes hundreds of millions of pages, and responds to tens of millions of searches each day.
In order for a Search Engine tell you where a file or document can be found, it must first be found and indexed. To find and index the information on the hundreds of millions of Web pages that exist on the internet, Search Engines employs special software robots, called spiders, to build lists of search terms found on these Websites.
When a spider is building its lists, the process is called web crawling.
In order to build and maintain a useful list of search terms, the Search Engine's spiders have to look at a lot of web pages. How does a spider start its travels over the Web?
Well, the usual starting points are lists of heavily used servers and very popular web pages.
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