A compatibilist is a soft determinism or the position or view that causal determinism is true, but we still act as free, morally responsible agents when, in the absence of external constraints, our actions are caused by our desires. Compatibilism does not maintain that humans are free.
Incompatibilism is the thesis that free will is incompatible with the truth of determinism. Incompatibilists divide into libertarianism, who deny that determinism is true and hard determinists who deny that we have free will.