While developing the GIMP
(GNU Image Manipulation Program) a few years back, Spencer Kimball and
Peter Mattis decided that it might be fun to write a user interface
toolkit to go along with it. And so they created GTK+ (the GIMP Toolkit)
– a library of “widgets” that makes it easier for developers to build
GUI-based application. A widget is one of the various components of a
graphical application; a toolbar, for example. The widgets provide
programmers with pre-built dialog boxes, windows, menu bars and other
GUI components. Having a pre-built foundation for these user interface
components greatly speeds development of GUI applications and also
enables applications built with those widgets to share a common “look
and feel”.