Help!! Question about Steemit Rewards

I'm still relatively new to Steemit and was wondering how the different Rewards work.

Specifically, what do the following mean?

1. Power Up 100% (Does it mean 100% is paid out?)
2. 50/50 Split
3. Decline Payout

Lastly, are the rewards paid in Steem Dollars?

Thanks for the help!