Core Animation Layer - iOS Programming: The Big Nerd Ranch Guide - page 613

Notice in Figure 22.2 that each view has a layer and each view is its layer's delegate.
We'll come back to the delegate relationship later in the chapter.
So what's the reason behind having views and layers? Remember that UIView is a sub-
class of UIResponder . A view is really an abstraction of a visible object that can be in-
teracted with on the screen, wrapped into a tidy class. A layer, on the other hand, is all
about the drawing.