Chapter 8: Search Engine

A search engine is a set of programs which are used to search for information within a specific realm and collate that information in a database. People often use this term in reference to an Internet search engine, a search engine which is specifically designed to search the Internet, but search engines can also be devised for offline content, such as a library catalog, the contents of a personal hard drive, or a catalog of museum collections. Search engines help people to organize and display information in a way which makes it readily accessible.
There are three aspects to a search engine: crawling, indexing, and searching. When a search engine crawls, it looks for new content which was not present during the last crawl, including updates to files and web pages. Then, the programs index the information, pulling out specific keywords to categorize it. On the Internet, for example, indexing relies heavily on keywords in web pages, and meta tags which provide information about the page.

 


The example of search engine.

reference : http://www.wisegeek.com/what-is-a-search-engine.htm