cl-gtk2 is the GUI library for Common Lisp. cl-gtk2 is based on Gtk+ GUI library and is Common Lisp binding for it. cl-gtk2 allows you to create graphical user interfaces for Common Lisp applications.
As Gtk+ is based on object system GObject, cl-gtk2 is based on a binding to this object system called cl-gtk2-gobject.
cl-gtk2 provides a thin wrapper around Gtk+ functionality, mostly retaining the same set of classes, properties and methods.
The important parts of Gtk+ are: