Lightning channel backups also known as static channel backups are backup files that only need to be updated when an LN node opens or closes a new channel. These backup files are a failsafe to record the state of a Lighting channel in case of data loss. They allow the Lighting node user the opportunity to attempt to get the latest channel state from the various remote peer peers they had connections with prior to the shutdown of the Lightning node.

Static channel backups allows a node that has potentially lost some of its state to encourage its peer to initiate a channel close. Since the peer should still have the most recent state, it can close the channel using that state and allow both nodes to receive their most recent balances.

@ref https://thebitcoinmanual.com/articles/ln-channel-backup/