Robots.txt is a file used to instruct web robots, or "bots," on how to crawl and index a website. Robots.txt is a simple text file placed in the root directory of a website, and it is used to communicate the crawling and indexing rules for the website to web robots.
The Robots.txt file is not mandatory, and its use is voluntary. However, it is a widely-used and accepted convention, and most web robots and search engines support it.
The Robots.txt file consists of instructions called "directives," which specify the rules for crawling and indexing the website. The directives can determine which pages or directories on the website should be crawled and indexed and which pages or directories should be excluded. Using the Robots.txt file, website owners and administrators can exclude sensitive or private pages from being crawled and indexed. They can also prevent web robots from overloading their website with excessive requests.