Glossary
What is cold storage?
In one sentence
Cold storage means keeping private keys completely offline, so a remote attacker has no path to them at all.
Cold storage is the opposite of a hot wallet. The keys are generated and held on a device with no internet connection — most commonly a hardware wallet, sometimes a dedicated offline computer, occasionally a seed phrase written down and no live wallet at all.
Because there is no network path to the key, remote attacks do not apply. The realistic threats become physical: someone finding your seed phrase, a fire destroying your only backup, or you being tricked into typing the phrase somewhere.
Cold storage is deliberately inconvenient, and that is part of how it works. Moving funds takes a deliberate physical action, which also protects you from impulsive decisions and from transactions signed in a hurry.
For example
A hardware wallet in a drawer with its seed phrase stored separately is cold storage in practice.