I know both are deeply involved, but I like to think of Thelema in two aspects:
a) True Will; discovering your true nature and doing your True Will. The knowledge of all aspects of your own being. The practical work the A.'.A.'. system proposes we do. "Who am I? Where am I going?".
b) A religious and philosophical system, including the ideas of Secret Chiefs, Aeons, praeter-human beings, feasts, prophets, a new formula, Holy Books mysteries and interpretation, thelemic morals, etc. "From where did I come?" Things more inclined to make people act like fanatics (I don't say this is the general rule, but it happens a lot, don't you think?).
I would call the Do-what-thou-wilt Thelema and the attached "religious" system Crowleyanity. (I am not using this word as an offense.)