A backup of a set of specified files, often the entire contents of a disk, regardless of when they were last modified. A differential backup is a backup of a set of specified files, often a disk’s entire contents, that includes only those files modified since the last full backup. A restore operation would involve the full backup plus the differential backup. An incremental backup is a backup of a set of specified files, often a disk’s entire contents, that includes only those files modified since the last incremental backup. In the latter case a restore operation would involve the last full backup plus all the subsequent incremental backups.