Nero BackItUp is a program for backing up and restoring data. Nero BackItUp saves files (file backup), as well as programs and operating systems (drive backup). 
Open files can be backed up with the shadow copy feature, while you continue to work on the file. You can burn the backup to a disc, save it to a hard drive or removable medium, or use an online storage. With Nero BackItUp you can verify at any time that the backed up data is complete and correct.
Use Nero BackItUp to schedule backups, e.g. for regular data backup that are executed automatically. You can also use Nero BackItUp to set up the Autobackup feature, which automatically backs up monitored folders.
Nero BackItUp ImageTool is another tool for backing up files and drives. The Nero BackItUp ImageTool is included on the bootable disc that you can create with Nero BackItUp. With the Nero BackItUp ImageTool, you can back up and restore drives. This particularly lends itself to backing up on otherwise active drives, since such drives are inactive when booting the Nero BackItUp ImageTool. 
Nero BackItUp SyncTool is a tool for syncing folders. It is created with Nero BackItUp and stored either on hard disk drive, removable medium or optical disc. Nero BackItUp SyncTool can be started from this medium on any computer; Nero BackItUp doesn’t have to be installed to start Nero BackItUp SyncTool. 
Shadow Copy
A shadow copy is a snapshot of a file at a certain point in time. The advantage is that you can keep working with this file while the backup program, e.g. Nero BackItUp, backs up the file in the background. This feature is particularly relevant when you want to save system files, which are modified continuously by the system.

About Nero BackItUp