How does a Search Engine work?

What is a Search Engine? A search engine is a software program which searches for sites based on the words that you give as search terms. Search Engines and Web Directories are not same, although the term 'search engine' often is used interchangeably.
How Search Engine works? Search Engines automatically creates web site listings by using 'spiders' that 'crawls' web pages, index their information and optimally follows that sites link to other pages. Spiders return to allready crawled sites on regular basis to check for any updates or changes and every thing that these spider finds goes into the search engine database. on the other hand, web directories are databases of human compiled results. Search engines includes detailed processes and methodologies, and are updated all the time. All search engines go by this basic process, but because there are differences in search engines, there will be some differences in the search results. 1. The searcher types a query into the search engine, 2. search engine software quickly sorts through literally millions of pages in its database to find matches to this query. 3. the search engine results are ranked in the order of relevancy.

Examples of Search Engines: There are n number of great search engines out there for you to choose from. Google, bing, Yahoo Search, altavista, cuil, exite, hotbot, AlltheWeb, galaxy, Windows Live Search, Aol Search(powered by google), GigaBlast are to name a few, there are many more avaliable.