Search Engine is work as answer machine. When a person perform an online search, search engine does two things: firstly, it returns only those results that are useful and relevant to searcher’s query and second, it ranks those results according to the popularity of the websites serving the information. Search engine is a software system that mainly designed to search for information on world wide web. The information given by search engine may be images, mix of web pages and other type of data and files.

Search engines are special sites on the Web that are designed to help people find information stored on other sites. A search engine operates some steps (I) web crawling (ii) indexing (iii)searching. A web crawler started with the list of URLs for visit. When the crawler visit these URLs, it identifies all the hyperlinks in the page and add them to the list of URLs for visit, it is known as crawl frontier.

The main purpose of indexing is to optimize performance and speed in finding relevant documents for search query. The web search query is a query that when a user enters into search engine to satisfy her or his information requirements. When the user enters any query into search engine , the engine examine its index and providing a list of best matching web pages related to user’s need.