Tell Me What is Steem...!

A few months ago steem words still rarely encountered in social media, not so steal the attention, even if I read only because of interest in the content alone, some friends in social media often post his writings through steem, I just think that it is a kind ordinary blogs where people often create posts, from a mere hobby to who seek or reap the benefits of ad clicks.
as time goes by steem the more often I find in social media, people are more incentive to talk about steem, talking dollar, making community or gathering, and some even associate bitcoin or blockchain.
Here's where there's a curiosity about what's with steam, how can steem be valuable, can it be mined like bitcoin? or even be in trading? if this is so incredible, something very interesting to learn.
Recently very little that I know the problem steem, hopefully have a lot of time to learn.