The work of the search engine is divided into three stages, i.e. crawling, indexing and retrieval. 1) Crawling The search engines have the web crawler or spiders to perform crawling. The task of crawler is to visit a web page, read it and follow the links to other web pages of the site. Each time the crawler visits a webpage it makes a copy of the page and adds its URL to the index. After adding the URL it regularly visits the sites like every month or two to look for updates or changes. 2) Indexing In this stage, the crawler creates the index of the search engine. The index is like a huge book which contains a copy of each web page found by the crawler. If any web page changes the crawler updates the book with new content. So, the index comprises URL of different web pages visited by the crawler and contains the information collected by the crawler. 3) Retrieval This is the final stage in which the search engine provides the most useful and relevant an...