Contains classes that are graphical in nature.  Each one displays something to the user in a visual manner.
The classes in the top package don't have any render-specific code in them. Each is extended in a sub package and rendered using a specific graphics library or language.  For example, a set of classes are extended for drawing to the screen using OpenGL, while another set draws to a file using PostScript commands.  Each set is generically assignable using the base classes in the top package.
The gui sub package contains custom dialogs and components.