Both the source and destination volumes need to be mounted on your Mac. It can create a copy of any image or volume that can be mounted on your Mac. Provided the source for the clone was a bootable startup drive, then the destination will generally also be useable as a bootable startup drive, which is pretty darned convenient. We often think of this as cloning a drive, so you have an exact copy for backup or archiving purposes. Disk Utilityin all of its incarnations, has always had a restore function, a way to copy a disk volume or image file to another volume, creating an exact copy.
