A web search engine is designed to search for information on the WWW (World Wide Web). The search results are usually presented in a list of results.
What is web search engine?
Search engine is the software program that searches for websites based on the input search string text. Search engines look through their own database of information in order to find what you are looking for. Search engines perform several activities in order to deliver search results – crawling, indexing, processing, calculating relevancy, and retrieving.
How search engine works?
1. Search engines crawl the Web to see what is there. This task is performed by e piece of software, called a crawler or a spider (or Googlebot, as is the case with Google). Spiders follow links from one page to another and index everything they find on their way. There are billions of pages on the web, so it is not possible for crawler to visit each link of your site daily. It may take time to crawl your pages. Keep in mind that crawlers do not see images, Flash movies, JavaScript, frames, password-protected pages and directories.
2. After a page is crawled, the next step is to index its content. The indexed page is stored in 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.
3. When a search request comes, the search engine processes request by compares the search string in the search request with the indexed pages in the database. There are millions of web pages contains the search string, the search engine starts calculating the relevancy of each of the pages in its index to the search string.
There are various algorithms to calculate relevancy. Each of these algorithms has different relative weights for common factors like keyword density, links, or metatags. That is why different search engines give different search results pages for the same search string.
All major search engines, like Yahoo!, Google, MSN, etc. periodically change their algorithms and if you want to keep at the top, you also need to adapt your pages to the latest changes. SEO is one of the process for website optimization.
4. The last step in search engine activity is retrieving the results. It simply display relevant information on the web in endless web pages for users.
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Sources : www.webconfs.com, websearch.about.com, www.wikipedia.org
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