A software program that collects information taken from the content of files available on the Internet and places them in a database that Internet users can search in a variety of ways. The search results then provide links back to the original location of the files matching the user's search.
A service which collects web-pages or resources via a computer program (crawler, spider, robot, etc.), indexes the collected files, and provides a searchable database of collected files. Examples: Google, Yahoo.