Also known as Spider or Robot, a crawler is a search engine program that "crawls" the web, collecting data, following links, making copies of new and updated sites, and storing URLs in the search engine's Index. This allows search engines to provide faster and more up-to-date listings.
A Web crawler, sometimes called a spider or spiderbot and often shortened to crawler, is an Internet bot that systematically browses the World Wide Web and that is typically operated by search engines for the purpose of Web indexing (web spidering).