Differential backupstores the data changes as they occurred since the last full backup. The process is similar to incremental backup, but differs in how data is stored. In the first differential backup, a full backup is made. It forms the reference and is used for the comparison of the following differential backups. In the second backup, only the data that has changed since the full backup is saved. In the third backup, the changed data of the third backup is added to the data of the second backup, etc.
The technique of differential backups requires less storage space than full backups and can be used to restore data in a relatively short time.