Backup Folders are part of the Cloud Backup service. When a user backs up a device, a backup folder is automatically created in the portal, to contain the device's backups.
By default, when folders are created in a portal, they are assigned a name based on the device's name. For example, if a device is named JohnS, then this device's files will be backed up to a folder called JohnS, and its cloud files will be stored in a folder called JohnS-CloudFiles followed by a number. You can add new folders manually and can edit their properties.