Coinbase has no control over any cryptocurrency accounts besides their own. Each cryptocurrency user generates a private key that becomes a wallet and is used

Coinbase has no control over any cryptocurrency accounts besides their own. Each cryptocurrency user generates a private key that becomes a wallet and is used to sign transactions. These signed transactions are then broadcast to the internet for balance keeping nodes to keep track of. They do it in a globally distributed manner (no central entity) and earn rewards for their work (like collecting a tiny fraction of the transaction as a fee). The private key is never disclosed to anyone.