The aftermarket auto warranty is designed to protect your car, or more specifically to protect you when your car breaks down or wears down.  It is a warranty or a service contract that is bought at an additional price to the vehicle purchase and it differs from all other warranties for the said reason – it is the only warranty that you must purchase.  It is also the only warranty that you can get at any other time after the first purchase of the car; more so, you can purchase this warranty at any other dealer or service provider different to the dealer that you buy the car from.
The aftermarket auto warranty is different from all other warranties also for the very reason that it is not really a warranty.  Since you are paying for this coverage, you could say that it becomes more of a guaranteed service that is valid for the terms of purchase agreed upon.  Most times this term of purchase simply means the type of coverage (limited or fully comprehensive), the period of coverage, or the distance covered in terms of mileage.  The aftermarket auto warranty is simply designed to extend the coverage of an existing warranty or to provide coverage for a vehicle where there formally existed none.