A hot wallet is connected to the internet: a mobile app, a browser extension, an exchange account. It is convenient and it is exposed. A cold wallet keeps keys on a device that never touches the internet — a hardware wallet or, in the extreme, a phrase written on paper.

The practical arrangement most holders settle on is a hot wallet for spending amounts and a cold wallet for savings, with an amount split that reflects how much loss would actually hurt.

• Custodial: the exchange holds the keys. Recovery is possible if you forget your password, but you are exposed to the platform's solvency and policies.
• Self-custody: you hold the keys. Nobody can freeze or lose your funds but you, and there is no reset button.
• The trade-off is counterparty risk against personal responsibility. There is no option without one of them.

Twelve or twenty-four words regenerate every key in the wallet on any compatible device. That makes the phrase, not the hardware, the thing being protected. Anyone who reads it owns the funds instantly and irreversibly.

• Never photograph it, type it, or store it in a password manager or cloud note.
• Write it on paper or stamp it into metal, and keep at least two copies in separate physical locations.
• No legitimate support agent will ever ask for it — that request is the single clearest sign of a scam.

Sending the right token over the wrong network is one of the most common ways funds are lost. USDT on Ethereum and USDT on Tron are not interchangeable, and an incorrect network choice usually cannot be reversed. Send a small test amount first on any new address or network — the fee is trivial compared with the alternative.