SEO

https://support.google.com/webmasters/answer/1663419?hl=en

By using a robots.txt file.

Using Robot.txt file.

User-agent: *
Disallow: /

The "User-agent: *" means this section applies to all robots. The "Disallow: /" tells the robot that it should not visit any pages on the site.

SEO stand for Search Engine Optimization which is used for getting traffic from the organic or natural search result on search engine.

robots.txt file is used.

Yes you can do it from robots.txt file, you have to write just two lines code. For example if https:// www.xyz.com is your website and you want to disallow abc.html page then you have to write in robots.txt file
User-agent: *
Disallow: /abc.html