The backup folder is where backups can be found.
A backup is an image(copy) of a connected device, which is being preserved for data retrieval purposes. You may browse the backup content.
How are backups named (by default):
[manufacturer] [model] ([MM/DD/YYYY] [HH:MM:SS] [AM/PM])
Example: Nokia 5800 XpressMusic (7/30/2010 2:17:58 PM)
You can choose a different name on your own.