Cold storage refers to the practice of storing Bitcoin or other cryptocurrencies in a way that is not connected directly to the internet. This is typically done for security reasons, as it reduces the risk of the cryptocurrencies being stolen by hackers. Cold storage can take many forms, such as storing the private keys for a cryptocurrency on a piece of paper or a hardware device that is not connected to the internet. Some people also use offline computers or "air-gapped" devices, which are not connected to the internet at all and are therefore considered more secure. Cold storage is typically used for long-term storage of cryptocurrencies, as opposed to hot wallets, which are connected to the internet and are used for more frequent transactions.