The physical coin is for safe storage and yes you own it. They mail it to you. Right now their is a limit of 2 coins per customer. When you want to spend some you mail them back in and they get deposited back into you e-wallet. Far in the future I imagine you will be able to get different valued coins and spend like cash as well but for now Vault 51 is a security measure to make sure your coins don't get hacked and stolen. You don't have to buy a coin you can buy storage for coins you already own as well.