If you are driving someone else's car, their insurance covers you while you are driving their car, as long as you:
If you have an accident while driving someone else's car, you'll need to present proof of insurance. It's a good idea to make sure you have this available to you before borrowing a car.
If the car's owner doesn't have insurance, there is coverage under your own policy to protect you. There are some criteria to be met; coverage won't extend to a vehicle owned by someone else in your household. Not all coverages on your own vehicle are provided and, while the covers vary by province, third party liability cover extends in all provinces.