So i know brute force means like you try all the combinations..
1. But its a computer entering each one etc over and over right? And not like a person doing it manually right? Now with brute force, is it a program that does it or is it a computer?

Theoretically, both is called bruteforcing.
But if you'd want to try to bruteforce a mnemonic (or a password or whatever), i'd recommend you use a computer for that.
~snip~