A robots.txt file is a text file that can be placed in the root directory of a website to tell web robots (also known as web crawlers or spiders) which pages or files on the website should not be processed or indexed.
The default robots.txt file for a web server usually allows all web robots to access all pages and files on the website. It typically looks like this:
User-agent: * Allow: /
The User-agent: * line indicates that the rule applies to all web robots. The Allow: / line indicates that all pages and files on the website should be allowed to be accessed and indexed.
You can customize the robots.txt file to block specific web robots or to block access to specific pages or files on your website. For example, you might use the Disallow: directive to block access to a particular directory or file, like this:
User-agent: * Disallow: /private/
This would block all web robots from accessing the /private/ directory on your website.
It's important to note that web robots are not required to obey the instructions in a robots.txt file, so it's not a foolproof way to block access to your website. However, most web robots will respect the instructions in a robots.txt file as a matter of etiquette.