Google is an Internet search engine founded in 1998 by Larry Page and Sergey Brin, two Stanford Ph.D. candidates, who developed a technologically advanced method for finding information on the Internet.
Google uses an algorithm called PageRank to rank web pages that match a given search string. The PageRank algorithm computes a recursive figure of merit for web pages, based on the weighted sum of the PageRanks of the pages linking to them. The PageRank thus derives from human-generated links, and correlates well with human concepts of 'importance'.
Google employs a farm of about 3500 Linux computers to answer search requests and to index the web about once a month. The index database is several terabytes large.