Help Me Understand Steemit

Hello Steemers. My name is Arthur and I live in Southern California. I have been on steemit for a few months but still don't understand completely how everything works. I post photography of different sunsets, clouds, the sky, and other beautiful views or places that I come across. I usually use a DSLR Nikon Camera but the photos on my account are mostly taken from my iPhone 6s which I think gives it that everyday lifestyle feeling to it. Maybe that's just me but lets get into this topic for today.

I am confused about stuff like how do I cash the Steem, Steem Dollars, or Steem Power out to real US Dollars. I was told that the way you get Steem Power is by having Steem in your account which builds up Steem Power. I am not 100% sure about that but if you know, please comment on how Steem Power works. Another Question that I have is why does Steemit have Steem Dollars and Steem power and what is the difference? How come there isn't just one Cryptocurrency in Steemit? How do I expand my account and grow bigger? Is the price for Steem the same for Steem Dollars? How do I buy Steem, Steem Dollars, or Steem Power (If Steem Power doesn't have anything to do with Steem or Steem Dollars)? Do I need to invest in Steemit to grow bigger? These are just some of the questions that I have. I am soon going to be an investor in Steemit and other cryptocurrencys as I learn more about them and gain more knowledge. If you have been on Steemit for a long time or are an expert in the fields of Steemit or any Cryptocurrency please leave a comment and I hope you tag along on my journey across Steemit. Thank you.