How does a Search Engine Work?

Search engines perform several activities in order to deliver search results.

• Crawling - Crawling is process of fetching all the web pages linked to our website. This task is performed by a software called a crawler or (a spider or Google bot, in case of Google).
• Indexing - Process of creating index for all the fetched web pages and keeping them into a giant database from where it can later be retrieved. Essentially, the process of indexing is identifying the words and expressions that best describe the page and assigning the page to particular keywords.
• Processing - When a search request comes, the search engine processes it, i.e., it compares the search string in the search request with the indexed pages in the database.
• Retrieving Results - The last step in search engine activities is retrieving the best matched results. Basically, it is nothing more than simply displaying them in the browser. Search engines such as Google and Yahoo! often update their relevancy algorithm dozens of times per month.