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The amount of SteemPower someone has determines the weight of their vote.

And when someone with that much steemPower votes they also get a cut of the proceeds when there is payout?

Part of a payout is writers rewards and part is curators rewards (the people who have voted). Greater SteemPower increases the overall payout. And it increases ones share of curation rewards.
It does not take away from the writers payout. Does that answer what you asked?

and weight determines value? so I could theoretically buy a bunch of steem and create great power here without doing any real work for it? Or am I missing a point somewhere? Yes I am a noob, whopping 4 posts and all.

Well, yes. You have to commit that Steem to SteemPower though, which locks it up for quite a while. Payout over 13 months if I remember correctly. Well, long.

You're 4 posts ahead of me, so you'll do fine. Me, I'm the king of procrastination...