Intuition was designed with two major goals in mind.  The first is to give
users a friendly and consistent environment to control the functions of
the Amiga operating system and its applications.

The second goal (the big one) is to give application designers a graphical
user interface toolkit that manages all the complexities of sharing the
system with other programs that may be running at the same time.  Since
the Amiga is a multitasking computer, many programs can reside in memory
at the same time sharing the system's resources with one another. Programs
take turns running so that, from the user's point of view, it appears that
many programs are running simultaneously.

On a multitasking computer like the amiga, the user interface design must
allow the user to control many programs with just one monitor, one
keyboard, and one mouse.  (Imagine driving many cars simultaneously with
one steering wheel.)  Intuition supplies the tools needed to solve this
problem.