Search engines are programs that search documents for specified keywords and returns a list of the documents where the keywords were found. A search engine is really a general class of programs, however, the term is often used to specifically describe systems like Google, Bing and Yahoo! Search that enable users to search for documents on the World Wide Web.
Web Search Engines
Typically, Web search engines work by sending out a spider to fetch as many documents as possible. Another program, called an indexer, then reads these documents and creates an index based on the words contained in each document. Each search engine uses a proprietary algorithm to create its indices such that, ideally, only meaningful results are returned for each query.
As many website owners rely on search engines to send traffic to their website, and entire industry has grown around the idea of optimizing Web content to improve your placement in search engine results. Learn more about search engine optimization (SEO) in this Webopedia’ definition.
Common Search Engines
In addition to Web search engines other common types of search engines include the following:
- Local (or offline) Search Engine. Designed to be used for offline PC, CDROM or LAN searching usage.
- Metasearch Engine: A search engine that queries other search engines and then combines the results that are received from all.
- Blog Search Engine: A search engine for the blogosphere. Blog search engines only index and provide search results from blogs (Web logs).