What is a user interface? This sweeping phrase covers all aspects of
communication between the user and the computer.  It includes the
innermost mechanisms of the computer and rises to the height of defining a
philosophy to guide the interaction between human and machine.  Intuition
is, above all else, a philosophy turned into software.

Intuition's user interface philosophy is simple to describe:  the
interaction between the user and the computer should be consistent, simple
and enjoyable; in a word, intuitive.  Intuition supplies the tools needed
to turn this philosophy into practice.

Implicit in this philosophy is the idea that the user interface should be
graphical.  A graphical user interface, or GUI, is a visually oriented
method of communicating with a computer in which system resources are
represented by pictorial symbols that can be manipulated with a pointing
device such as a mouse.  Other types of user interfaces are possible such
as the Amiga's Shell in which text commands are entered by typing them at
the keyboard.  For more information about user interfaces, refer to the
Amiga User Interface Style Guide.

 Elements of the Amiga Graphical User Interface System 
 Goals of Intuition