Backup
An incremental backup only copies the data that has changed since the last incremental backup.  This makes each backup quicker, because we are only copying what has changed since the last backup.  To bring the data back, if the main copy of the data is lost, we need the last full backup, as well as all of the incremental backups that have been done since then.  This means that bringing data back from an incremental backup is slower and more risky than differential or full backups.