STEEM = Cryptocurrency where you can trade on an exchange

Steem Backed Dollar (SBD) = You can buy more STEEM (through the market place or an exchange) or you could power up your Steem Power (SP)

Steem Power (SP) = Allows you to increase your influence on upvoting other's posts and increases your curation rewards. It also accrues 1.5% interest each year.

To earn more, write some quality pieces that people will upvote or comment on things that people post and if they upvote you then you might get some dollars or cents out of it, which when you receive the payment in SBD and SP (or just SP depending on which option you have selected) you can then 'power up' your SP.

Hope this helps! :)

Keep on Steemin in the free world!