What is a Search Engine ? An internet-based tool that searches an index of documents for a particular term, phrase or text specified by the user.  Commonly used to refer to large web-based search engines that search through billions of pages on the internet. Some get their data from other search engines. Click here for the search Engine Relationship Chart Common Characteristics: Spider, Indexer, Database, Algorithm Find matching documents and display them according to relevance •Frequent updates to documents searched and ranking algorithm •Strive to produce “better”, more relevant results than competitors What Search Engines Are the Most Popular? Figures below show what percentage of US internet users accessed the corresponding sites at least once during a given month.  Counts only search-specific visits.  (Nielsen//NetRatings – June 2004) 1.Google – 41.6% 2.Yahoo – 31.5% 3.MSN – 27.4% 4.AOL – 13.6% 5.Ask Jeeves (now Ask.com) – 7.0% How do search engines find your websites ? Spider “crawls” the web to find new documents (web pages, other documents) typically by following hyperlinks from websites already in the database Search engine indexes the content (text, code) in these documents by adding it to their huge databases and periodically updates this content Search engine searches its own database when user enters in a search to find related documents (not searching web pages in real-time) Search engine ranks resulting documents using an algorithm (mathematical formula) that assigns various weights to various ranking factors •