I now know how steem works and it took about 10 minutes. Here's what you need to know so you can quickly understand the money involved!
Let me explain first the difference among steem, steem dollars, and steem power.
How Steem Works
First thing to know is that steem has no real value in the steemit.com ecosystem. It's a currency that is traded on open platforms and is volatile just like the others you've probably heard of. People trade steem on coinbase, poloniex and others because of speculation.
As a user of steemit.com, you would use steem to either cash out your steem dollars or steem power OR to buy into either of the two.
Like I said, steem is volatile and one shouldn't hold steem in their account and do nothing with it. Instead, trade steem for bitcoin or trade bitcoin to steem power and buy more influence in the steemit community..
Your steem can be used to purchase steem dollars or steem power or vice versa.
What are Steem Dollars
Steem dollars is the currency of the steemit economy, just like US dollars is the currency of the American economy. However, unlike steem, steem dollars have no value in the real world. They are used to give and receive value in the steemit community.
Geniously, the founders of Steemit pegged the steem dollar to the US dollar. That means it is a much more secure investment, just like the US Dollar (for now). It does not go up and down crazily in price like crypto currencies or some other digital assets. It is also more liquid that steem power (explained below) so it can be converted quicker to steem.
It also collects 10% interest from the new steem created (more on that in 
What is Steem Power
Basically put, steem power is a longterm investment in the steemit project!
When you invest in steem power you invest in your influence on the platform AND the other 90% of the newly created steem!
However, once your earnings are steem power by buying with steem or steem dollars, you can only convert that steem power back over a 13 week period. That just means it is not very liquid, but like I mentioned, it's a longterm investment.
Use steem power to save if you believe in steemit AND to have more influence on steemit.com
Keep Steeming to Learn More!
I have been on steemit for more than a week and it took me a while to really understand how the how Steem money works and how to turn it into Cash!
I learned simply by using the platform (and making a bit of money at the same time).
More Explanations of Steem, SBD and Steem Power
The original video that taught ME about steem was from
Andrew also generously did an interview from the great request of 
Disclaimer: I am new on steemit, so the info is as accurate as I know best. For further 100% accurate info, you should read the white papers on steemit.io