What is a crawler?

[Ranjita]

A crawler is a word given to Google's system that browses the World Wide Web. It is also called spider. The main purpose of the crawler is indexing your site.

[omthavertch]

crawler is the a robot of the search engine to index the site and every search engine has its bot to crawl the site

[sapnajha]

Crawlers and bots are more or less the same they are used to automate the work which is repetitive.
Crawlers are used by search engines to make a copy of the webpage in their database, consider a google bot / crawler visits your page then google will be having a copy of your webpage and analyze the page and rank them accordingly, Also they make a list of links available in your website and form a hierarchical order of webpages available, making one page as home and others as child pages. This type of crawling makes the search engines check for new pages available, so it can update its database.

[Jackandrew]

A crawler is a program that visits your web sites and reads all their pages and other information in order to create entries for a search engine index. It is also known as a web spider.

[jane18]

Crawlers are search engine's programs to crawl website and its pages.

[colnettella]

Crawlers are search engines spiders that crawls the pages and save it to their data base to show search engine results.

[AvniShergill]

Crawler refers to the program that visits website and reads pages and other information in order to index the page.

[rousellwall]

Well, Crawlers are also known as a Google Spider. They are programmed bot, they crawl websites and stores regarding information of website in their database.

[marclewis]

The program that visits web sites and reads their pages to create entries for a search engine index is called crawler.

[Ship497]

A crawler is a bot of search engine which index website pages.

[SammiRose]

Crawler is basically program who runs around to collect the websites datas to update in the Search Engines Databases

[Bharti Mahour]

Google's crawler helps to crawl the web pages to save in data base.

[janeleonard]

A crawler or a robot is a search engine program to visit the pages and index them in the database. It helps to retrieve the indexed information to display in the SERPs.