It's a new platform that has been around for a few months. It is open to all sorts of posts and is still in the process of defining what a true "Proof Of Brain" post is. There are no miners or airdrops and the only way to earn POB is through posting, commenting, and interaction. The tokenomics are related to BTC in that there will only be 21 million tokens total. Right now they are worth .92 Hive so POB is off to a grand start. :)