I haven't heard of tapmaster before, but tapster is a bartender (the one who controls taps of barrels cointaning alcoholic beverage). I think it means the same.

The difference lies in their strength. "Should" is the weakest. It implies that it's good to do something. It's good for suggestions. Example: "You should repair your bike. It would work better" "Must" is stronger. It means it's important for you to do something (obligation). Example: "You must repair your bike. It looks unstable and you might hurt yourself" "Have to" is the strongest. It means it's very important, or you were ordered by other people, to do something. Example: "You have to repair your bike. You can't ride on it until it is repaired. I forbid you". In practice it usually doesn't matter that much if you mix up these words, so don't worry. Hope it helps. Maybe other people will add something to it. Good luck. :)