The trinity of STEEM, SBD and SP is not so easy to understand, especially since SP doesnt really exist!
Well it of course exists, but it is derived from what is called VESTS.
There are a lot of them so Mv (megavests) is the convenient units to use and as a VERY rough approx. each Mv is worth about 1 BTC. At least for now. Of course over time the value of Mv is changing, and it has definitely grown since steemit was launched.
Now when you look in your wallet, it displays STEEM Power. How does it determine that? The answer is on steemd.com
steem_per_mvests
251.534
You will see that in the upper right corner and it is compounding like crazy rabbits.
The above number was what was there at 8:49 am, by 9:26 am
steem_per_mvests
251.577
So what? You might think gaining .043 is no big deal, but the big deal is that it is doing this all the time, 24hrs per day. Now 0.017% is a small gain, but it happened in less than an hour. And this number is what multiplies your Mv to come up with the amount of STEEM Power you have.
A key thing to note is that if you are powering down and if the steem_per_mvests goes up faster than the powerdown dilution, you will actually gain in STEEM Power while you are powering down! Of course, the source of all this, the Mv, you have is going down but if you need some liquid cash, powering down is a good way.
Just make sure you never put more money into Mv than you can afford as it is still in the risky stage. However, if steemit achieves any level of real world traction, then once you have 100x your weekly expenses in Steem power, well it means you can live indefinitely off of the power downs.
So, people can complain about whale this, unfair, that, etc. but if you view steem as a place to park funds long term that has a decent chance to keep growing, it is pretty good. Also, steemit is still very young and constantly being updated and as long as it keeps improving, it is a matter of time before reddit is challenged and after that...
another half hour:
steem_per_mvests
251.602
And remember each MV you have is multiplied by steem_per_mvests
James
P.S. If you want to support me, just upvote my crypto777 witness account #44 on https://steemit.com/~witnesses