Stacks is a layer 1 blockchain that lets you earn bitcoin through a process called stacking. It is intertwined with Bitcoin as they use a concept called Proof of Transfer to interact with Bitcoin. This is currently my favorite crypto to hold.
Stacks is currently only available in the US on OKCoin and KuCoin to my knowledge. Here is a referral link https://www.okcoin.com/join?channelId=600032174 to OKCoin so me and you will earn $10 of Bitcoin when you signup and trade at least $100!