On the Internet, a search engine is a coordinated set of programs that includes:

• A spider (also called a "crawler" or a "bot") that goes to every page or representative pages on every Web site that wants to be searchable and reads it, using hypertext links on each page to discover and read a site's other pages
  
• A program that creates a huge index (sometimes called a "catalog") from the pages that have been read
  
  

  • Search Engine
  • Search Engine works
  • Search Engine Approaches
  • SE Submission Tips
  • Looking at the Web
  • Building the Index
• A program that receives your search request, compares it to the entries in the index, and returns results to you.

An alternative to using a search engine is to explore a structured directory of topics. Yahoo, which also lets you use its search engine, is the most widely-used directory on the Web. A number of Web portal sites offer both the search engine and directory approaches to finding information.