Robots.txt file instructs web robots (typically search engine robots) how to crawl pages on their website. They help webmasters to allow and deny a certain portion of the web content. Robots.txt is very important on the website as it will block the crawlers from the part of the website which is not needed to be indexed. Robots.txt file also can contain the sitemap URL. Search engines such as Google / Bing / Yahoo use website crawlers, or robots that review all the content on your website.