Synopsis A search engine or search service is a program designed to extract/find web pages or information stored on the WWW. Search engines facilitate easy access to the desired information on the Internet or a corporate database or a personal computer. The strength and usefulness of a search engine depends on the relevance of the result it produces for a given query and the way such results are presented. There are several search engines available on the Internet, but all are not equally efficient. Different search engines employ different methods and criteria for web crawling, indexing Web pages, handling the query, ranking the results and presentation. However, all have the same objective of providing the most relevant results first and the least relevant later, in the quickest possible time. The business of search engines has assumed a level where a search engine is no more an additional component of a comprehensive web portal. Competition among the market players more fierce than ever with billions of dollors at stake. In their attempt to outperfom one another, search engine companies are coming up with several value added features and version of search services. This phenomenon has seen the emergence of various types of search engines, like domain specific search engines, customised search engines, networked and desktop search engines, collaborative search engines, meta search engines etc, powered with the capabilities for handling queries in multiple languages, searching results in multiple data formats, accommodating multiple technologies and platforms. This book discusses the concept of search engines and provides insights into various types of search engines and their applications.