Steemit??? What is it??

Steemit is new for me and I am struggling with it. The problem is, I actually want to know, how do you earn rewards on Steemit. I went through a lot of posts on Steem but they all gave different methods.
The first one was that you have to comment, the second post said that you have to upvote and then there was the third post which stated something completely different and so on.

I have a gut feeling that you are the one who knows the answer, you are the one who can actually help me out of it, out of what's taking away the peace of my mind; you are the one.

So guys, if you any website article or blog which can help me, please do tell me in the comments. Your support will really help me and it will be truly appreciating.

Thanks,