The LOCK file extension is used by various OS and software for locking a resource. The LCK file may not contains data, and only exists as an empty marker file, but may also contain properties and settings for the lock resource. LCK file prevents concurrent access to critical resources.
The LOCK file extension is used by Minecraft, an open-ended block construction game. The general name is session.lock. LOCK file includes part of the data for a Minecraft world. LOCK file saves a timestamp for when the world was last accessed.