It's a 1994 "standard" that requires voluntary compliance and the user-agent is a string set by the operator of the tool used to access your site.
https://en.m.wikipedia.org/wiki/Robots.txt
https://en.m.wikipedia.org/wiki/User-Agent_header
In other words, the bot operator can ignore your robots.txt file and if you check your webserver logs, they can set their user-agent to whatever they like, so you cannot tell if they are ignoring you.
This does not block anything at all.
It's a 1994 "standard" that requires voluntary compliance and the user-agent is a string set by the operator of the tool used to access your site.
https://en.m.wikipedia.org/wiki/Robots.txt
https://en.m.wikipedia.org/wiki/User-Agent_header
In other words, the bot operator can ignore your robots.txt file and if you check your webserver logs, they can set their user-agent to whatever they like, so you cannot tell if they are ignoring you.