Search Engine -  A search engine is a website that enables users to Query an Index of stored webpages gathered by a Crawler for information relevant to explicit criteria expressed via a Keyword or Search Terms. The Rank of information/websites upon the corresponding Search Engine Results Pages is obvious by relevancy as measured by the search engine's Algorithm and/or payment made to the search engine by indexed sites. Sites ranked solely by relevancy are known as Natural Listings or Organic Listings in contrast to Paid Listings.