What is an offline or air-gapped backup?
It is a backup copy that has no permanent network connection to your systems, so an attacker inside the network cannot reach it. Classic examples are tapes or removable disks that are written, disconnected and stored elsewhere, and dedicated backup vaults that open a connection only during a short, controlled window. Some cloud services call an immutable, separately managed copy a logical air gap: it is not physically disconnected, but it is out of reach of your normal admin accounts. Offline copies are slower to restore and need discipline, because someone must actually rotate the media, check that the job ran and keep track of what is where. For most small companies the realistic target is one copy that is either physically offline or immutable under separate credentials, tested by restore at regular intervals. A copy that sits permanently on a share the whole network can reach is not offline, however it is labelled.