This book provides a broad introduction to search engines by integrating five different perspectives on Web search and search engines that are usually dealt with separately the technical perspective the user perspective the internetbased research perspective the economic perspective and the societal perspective.After a general introduction to the topic two foundational chapters present how search tools can cover the Webs content and how search engines achieve this by crawling and processing the found documents. The next chapter on user behavior covers how people phrase their search queries and interact with search engines. This knowledge builds the foundation for describing how results are ranked and presented.