What does the towing number mean?

Does the subject want to ask "What does the tractor number mean?" The license plate number of the tractor. Tractor is a general large truck or semi-trailer pulled between the front and trunk with tools, that is, the front of the truck can be pulled away from the original trunk, and the trunk can also be pulled away from the original trunk. The car with driving ability in front is called tractor, and the car without driving ability in the back is called trailer, which is towed away by tractor. The tractor number is the license plate number of the tractor. The license plate number is a number plate to identify the identity of the vehicle. It consists of Chinese characters, English letters and numbers, issued by dmv.