A search engine that crawls uses

web crawlers or spider software

Explanation:

A search engine that crawls uses the web crawler or the spider software. And it also uses the server side jа vascript based crawlers and programming languages like Python and PHP. The search engine finds the content category through the meta keywords and directs the page to the index. The index contains details of similar types of pages, And each page has one category, and if category is not found which is rarest, a new category is being created.