Here's a video from @craig-grant that will explain Steem Power and voting structure.
https://steemit.com/steem/@craig-grant/steem-rewards-strategy
He's got a lot of great videos. There's one where he goes in depth about the differences of Steem, Steem Backed Dollars and Steem Power. There's a ton of great information out there in older posts that really speeds up the learning curve. Hope this helps!