GtkWindow — Toplevel which can contain other widgets
GtkDialog — Create popup windows
GtkMessageDialog — A convenient message window
GtkAboutDialog — Display information about an application
GtkAssistant — A widget used to guide users through multi-step operations
GtkInvisible — A widget which is not displayed
GtkOffscreenWindow — A toplevel to manage offscreen rendering of child widgets
GtkWindowGroup — Limit the effect of grabs