A container is simply a widget
that is able to contain another widget. The vast majority of widgets fall
into this class; obvious examples include GtkWindow,
GtkTable and GtkBox. Other
than this property they are exactly the same as any other widget, and may
be added to other containers as well as supporting child widgets of their
own. They are derived from the GtkContainer base
class, which is itself derived from the GtkWidget
class.