This is a fundamental conceptual shift. A cryptocurrency wallet does not store coins like a physical wallet stores cash. Instead, it holds cryptographic keys: a private key (like a super-secret password that proves ownership) and a public key (derived from it, like an account number). The coins themselves exist as entries on a decentralized ledger (the blockchain). When you "send" crypto, you're using your private key to sign a transaction that updates the ledger, moving the entry from one public address to another. Whoever holds the private key controls the associated funds on-chain. This is why "not your keys, not your coins" is a cardinal rule—if you don't control the private key, you're trusting a third party (an exchange) with your assets.
