Originally Posted by fishtar
And what is the heater box assembly. As in, what does it do?
The dummy term is the thing that provides heat to the inside of the car, you know so you keep warm in the winter or your windows don't freeze up?
As Rudy said, it's required for safety to have a working defroster.
Track cars usually have all that stuff removed, since heat or a/c isn't needed in a race car.