Cold wallets are either hardware wallets or single nodes designed to calculate transactions. These wallets are offline, meaning they provide greater security of your funds.
wallets (Trezor, Ledger) deserve special attention. Very simply put, a cold hardware wallet is a kind of a secure flash drive where all you wallet data is stored. Sure, you have to pay money for this type of wallet but it's worth it if you store from $2000 and more in crypto.
In order to access money on such wallet, you need a direct access to the hardware wallet; it's impossible to hack it remotely as the wallet is not connected to the Internet.
Hardware buttons on such devices ensure the protection of your funds even if your computer is virus-infected (to perform a transaction you need to push a hardware button).
By the way, you can buy Trezor wallet on fatcats.market
without converting your cryptocurrency funds to fiat: