From a buyers perspective (already bought the car via Kijiji)

The VR number sometimes refers to the vin number. If you don't know what it is, its a 17 digit registration number unique to your car. You'll find it on the dash, it can be seen through the front windshield.

The number is used to search the car, it will tell if the car has been in a major accident, or subject to recall. Many sellers I dealt with got the information and simply provided that to potential buyers. Car dealerships also provide reports. CarFax was the best known at the time we purchased a car.

One person in our household has an out of province (BC) number. Its simply a matter of not ever having access to a better phone plan. We've lived in NS for almost 10 years.