Search engines analyse the contents of Web pages and create lists of occurrences of word forms found in pages or their URLs, in the information that Web page creators provide about their pages (the pages' metadata), or in links to pages. This analysis facilitates and accelerates searching online using key words. Search engines also use sophisticated calculations to rank the results of searches in an attempt to present the pages that are most likely to be helpful to a user at the top of the results list. Many search engines also offer a number of specialised searching functions, and each search engine has its own particular syntax that must be learned in order to optimise searches.