What is Search Engine?
Search engine is a mechanism or a group of programs that search documents for a specified keywords from the world wide web.
How search engine works?
Search engines perform some activities so that it can deliver search results. Some of them:
Crawling – Crawling is a method of fetching all the web pages connected to a web site. This task is performed by a package, known as a crawler or a spider (or Googlebot, just in case of Google).
Indexing– Indexing is a method of making index for all the fetched sites and keeping them into database from wherever it will later be retrieved.
Processing – Processing is a method of comparing search strings in the search request associated with the indexed pages and display the results.
Some popular search engines
These are the popular search engines, besides there many search engines that many not be so well known but still serve millions of search queries per day. You may see The Search Engine List.