A garage door cable, better known as the door lifting cable, consists of one big steel wire that further contains small strands of wires in between.
This type of construction provides strength and flexibility at the same time. This wire is attached to the door lifting mechanism at one side and on to the weights from the other side. So, basically this cable keeps the door balanced at all times during the operation. Most garage door cables are located on the sides of the door/panels and they pass through the sides along with the pulley.