A backup type in which only files and folders that have changed since the last normal backup are backed up. Unlike an incremental backup, a differential backup does not clear the archive attribute for each file and folder. You can use differential backups in conjunction with normal backups to simplify and speed up the backup process.
If a normal backup is done on a particular day of the week, differential backups can be performed on the remaining days of the week to back up the files that have changed since the first day of the backup schedule.
Differential backups are faster than normal backups and use less tape or other storage media.
Differential backups are cumulative (unlike incremental backups), so when you need to do a restore, you need only the normal backup and the most recent differential backup. Differential backups take longer to complete than incremental backups, but they are faster to restore data from.