GTK+ and memory allocation

[joshua rh comcast net]

Hello,
       Since I've started gtk+ I've been wondering what happens to all the windows and stuff you don't explicitly destroy, do you need to destroy it? does gtk_main_quit do it for you?  Sometimes I've been told to use g_free on things and I know if you make things non-pointers they get destroyed when they go out of scope.  What about this:

GtkWidget widget;

&widget = gtk_window_new(GTK_WINDOW_TOPLEVEL);

is the space originally allocated to widget lost and replaced by that returned from gtk_window_new?

and what if you have this:

GtkWidget *widget;

widget = gtk_window_new(GTK_WINDOW_TOPLEVEL);

and you reach the end of it's scope (this was my original question), does it get destroyed by gtk+?

Thanks for your time,

Josh