<para>A <seecref="T:Gtk.Window"/> can be one of these types. Most things you'd consider a "window" should have type <seecref="T:Gtk.WindowType.TopLevel"/> ; windows with this type are managed by the window manager and have a frame by default (call <seecref="P:Gtk.Window.Decorated"/> to toggle the frame). Windows with type <seecref="T:Gtk.Window.Popup"/> are ignored by the window manager; window manager keybindings won't work on them, the window manager won't decorate the window with a frame, many GTK+ features that rely on the window manager will not work (e.g. resize grips and maximization/minimization).</para>
<para><seecref="T:Gtk.WindowType.Popup"/> is used to implement widgets such as <seecref="T:Gtk.Menu"/> or tooltips that you normally don't think of as windows per se. Nearly all windows should be <seecref="T:Gtk.Window.Toplevel"/>. In particular, do not use <seecref="T:Gtk.Window.Popup"/> just to turn off the window borders; use <seecref="P:Gtk.Window.Decorated"/> for instead.</para>