A web search engine is a software application which crawls the web to index it and provides the information based on the user search query. Some search engines go beyond that and also extract information from various open databases. Usually the search engines provide real-time results based upon the backend crawling and data analysis algorithm they use. The results of a search engine are usually represented in the form of URLs with an abstract. Apart from usual web search engines, some search engines also index data from various forums, and other closed portals (require login). Some search engines also collect search results from various different search engines and provide it in a single interface.
