This guide focuses on how search engines work, explains some of their limitations and highlights some significant features in the main search engines. Addresses for the major search engines are provided. There are many specialist collections of Internet resources in specific subject areas and this guide includes a section on how to find such collections in your subject area. A search engine is a facility that enables you to search the Internet for Web pages containing a particular keyword or combination of keywords that you enter. There are thousands of Internet search engines, each striving to index the millions of pages published on the World Wide Web.
Search engines are largely the work of robots rather than of human beings.
Other facilities typically include ranking of search results, limiting of search results by date, country or type, and groupings of sites by subject area. Search engines enable you to search millions of Web pages quickly for any subject that interests you. They are easy to use at a general level and usually produce references to some relevant Web sites quickly. Many search engines limit their coverage to about 50 million pages, only indexing the most popular sites comprehensively. For other sites they may not provide indexing below the level of the home page.