For the Air Vent SQP61 roof louver what does rain diverter throat mean?

Here is some information about the SQP61 Rain Diverter

The back of the vent (the side that faces the peak of the roof) is shaped like a triangle so the rain that comes down from the peak of the roof is deflected away from the center of the vent, unlike the SLP61 vent which goes straight across.