Bot

From HostPedia

Bots are also known as web spiders and web crawlers. Bots are programs that crawl the web to gather information of various sorts. The most common use of bots is by Search Engines like Google, Yahoo!, Live (msn.com) and others.

For example: The GoogleBot is designed to collect page information such as hyperlinks, URL structure and Keywords that appear on web pages, the information is stored in large databases so that people would be able to query them through the google website.