Domers are architectural protrusions coming from the sloping angle of the roof. Dormers have a window at the end of the protrusion, with a mini roof installed to shed water.
A gable on the other end sits underneath the roof, where the side of the roof meets at the peak on the first, second or third storey of a house. If an imaginary line is drawn between the bottom of the roof to the top, a triangle will be formed at the highest point of the roof.