It actually only 2. The steem and steem power are the same currency. Steem power is steem that you have "invested" to utilize the steem platforms. The more steem power you have the more your vote will be worth. You can power steem up into steem power at any time but it takes 13 weeks to transfer steem power tokens back into steem. Here is a link to a friends blog that explains whats in your wallet.
https://steemit.com/steemit/@davemccoy/quick-tip-what-s-in-my-wallet-simple-understanding-of-steem-steem-power-and-steem-dollars