A crawler reads the content from a page and usually stores this in a search engines database, called an index. From this index the search results are extracted when one has entered a keyword in a search engine. A crawler is also referred to as a robot or bot from a search engine. There are also other crawlers, like the Wayback-machines crawler, that just stores the content(also images) from a website to create a record of the internet. Many other type of crawlers also scour the internet on a frequent basis. Every search engines have its own crawlers.
Thats not true, Meta search engine doesn't have something like that , they just fetch their datas. And i don't get the meaning of this thread.