A brat is a submissive who purposefully misbehaves or acts out in ways against their Dominant’s wishes. This can be for attention, to test limits, or provoke punishment. This may be because they enjoy the humiliation aspect of being punished, or for purely masochistic reasons.
I don’t think all SAMs are masochists, but they’re kind of the brat of the bunch. They’re definitely trying to provoke their Dominant. As an accidental SAM, I can tell you it’s not always on purpose. I have SAM tendencies but don’t embrace the label because it’s not intentional when I do it. Some SAMs are driven by the punishment, others by the pain. When I’m in SAM mode, John Brownstone knows the worst (and also best) punishment for me is something that doesn’t cause physical pain. (And that’s why he’s the sadist.) I would say that the label of “brat” might be a SAM or it may be the person who wants their submission forced, or a combination of the two.