A View is a rectangular entity capable of drawing to the screen and receiving key and mouse events. Each View has a superview and zero or more subviews. A tree-like structure that contains Views. The way that View responds to mouse and key events and draws to the screen is determined by its location in the View Hierarchy. A Window can contain a title bar, a close button and a resize bar that functions like of those in other systems.
Windows are rectangular regions.
They can be transparent meaning that they appear to have a non-rectangular shape.