When your peers read your content and like it, they will upvote you. It is much like "like" on facebook, only here you get paid every time you are upvoted. Payment varies a lot. I just upvoted your comment now and you got about 0.1 steem from me. It will be paid out a week from now and you have to collect it in your wallet.

You will also recieve payment when you upvote your friends posts. That reward is smaller, but will give you more influence. It is called Steem power.

Just write some articles and post them. One very popular article is a post where you introduce yourself. Make some preperation and take a photograph of yourself with a note that says steemit and your username. That way everybody will know it is you and not a imposter. Tag the post "introduceyourself", it normally gives you quite much money.