It's a little bit confusing I understand but in the end everything = STEEM.
1 SBD = 1 USD worth of STEEM. (I know it's trading for more atm)
SP = STEEM but already staked (or powered up).
I did not want to mention all this to keep it it simple. It's hard enough sometimes to understand.
The STEEM we earn with blogging we can sell on the open market. The market today says that 1 STEEM = $4.35 USD.
And thank you, I'm really happy today :)