A motor vehicle title (also referred to by some as the "pink slip") is a legal form, establishing a person or business as the legal owner of a vehicle. So it shows who legally owns the vehicle.
Registration is different in that it is a something required by the state to show you have registered with them, paid any taxes or fees due. Registering your motor vehicle goes hand in hand with the titling process. As part of the registration process you typically receive a license plate and registration document or sticker to place on the windshield in some states so that the vehicle is shown that it is known to the state and roadworthy.
License plates are evidence that registration fees have been paid and are a means of readily identifying a vehicle and tracing ownership. In Florida the HSMV defines registration as evidence of having paid the registration tax and fees on a motor vehicle. It consists of a metal license plate, a validation decal, and a registration certificate.
Yes, to register a vehicle with your state's Department of Motor Vehicles (DMV) you must show proof of ownership and thus your name must be on the title of the vehicle. For example in New York State if you are registering a vehicle you bought from a private party you need to show the DMV acceptable proof of ownership with a title certificate and a bill of sale. You then would not only register the car but be applying for a title in your name since when you buy a car the title is signed over to you, the buyer.
Normally to place a car on your car insurance policy you do need to show proof of insurable interest. This usually means to an insurer that you have some ownership in the car so you may need to have your name added as a co-owner of the car to be able to place it on your insurance policy. It really depends upon the guidelines of your insurance provider. Some do allow parents to insure their child's car on their policy without being on the title while others will not if you are not a co-owner of the car.
On a title there can be two names on a title separated by and OR or. State laws differ however basically when registering a vehicle and the names are joined by the word "or," one owner can sell the vehicle without the other's signature or consent. "And" or a slash (/) requires the signature of each owner to sell the vehicle. So if you do get your name added to the title keep this in mind so you can determine how your name should be added.
In most states even if you are listed as a co-owner on the car your son could register the car himself in his own name.
You also would need to check into your state laws on what proof of insurance is needed to register the car. In some states the insurance just has to be on the vehicle and does not necessarily have to be in the car owner's name. In other states the car owner's name must be on the proof of insurance. For example in Texas, where you register your vehicle with the County Tax Assessor, they state that the car proof of insurance shown must be in the owner's name for the vehicle to be registered.
So to see if you need to be added to your son's title as a co-owner to have insurable interest in it to place his car on your car insurance policy speak to your agent. Or if you are shopping around for the best car insurance prices ask the insurance carriers that you get quotes with what their underwriting rules allow in this situation. You also should check with your state's DMV to make sure they would accept insurance in your name for your son's car (if you end up leaving the title in his name only).