.BACKUPDB File Extension
File TypeTime Machine Backup Folder
What is a BACKUPDB file?
Backup folder created by Apple Time Machine, a backup utility included with Mac OS X 10.5 (Leopard); named "Backups.backupdb" and is often the only folder on the backup drive.
Because Time Machine uses the "backupdb" folder for storing incremental backups, it should not be modified by the user. Instead, use the Time Machine application to view backups and restore files.