They both specify a map center and how big the box is.
So why use both?
Some function in MKMapview use one and some use the other
(MKCoordinateRegion)regionThatFits:(MKCoordinateRegion)region(MKMapRect)mapRectThatFits:(MKMapRect)mapRect edgePadding:(UIEdgeInsets)insets
What's their difference?
More importantly, which one we should use to set the region we see?
There is no regionThatFits:edgePadding: by the way.