Question about hash changing

Well I've been browsing a few threads and I've noticed in almost all of them, people are mentioning 'changing your hash' or something like that to prevent ban. Can anyone explain what is meant by that, sorry if the question has a straight-forward/obvious answer?

It changes the MD5 hash, but if somethings detected, it won't really help..

I see, which file exactly do you need to change and what do you change it to?