Human errors of this type are undetectable to the backup process and data may be permanently lost if it is not recovered within a complete backup cycle. In a full backup, all of the data is copied. This process takes the longest time and requires the most backup media, but it is often the easiest method to restore lost data. Incremental backups only copy the data that has changed since the last incremental backup. This method takes the shortest time, but is the hardest to restore data because all incremental backups since the last full backup must be applied to restore the data to the most current state.
Differential backups copy all the data which has changed since the last full backup.
This is a compromise procedure which simplifies data restores at the price of increased backup time over incremental backups. Only the last differential backup need be applied to the last full backup to restore the data to the most current level. After backup is complete, the copy of the data needs to be stored in a safe location. It is dangerous to store the backups in close proximity to the data being backed up. If you have your backups stored in your office with your PC a small fire or water leak could destroy everything.