What it is:
Glade is a RAD tool to enable quick & easy development of user
interfaces for the GTK+ toolkit and the GNOME desktop environment.
The user interfaces designed in Glade are saved as XML, and by using
the GtkBuilder GTK+ object these can be loaded by applications
dynamically as needed.
By using GtkBuilder, Glade XML files can be used in numerous
programming languages including C, C++, C#, Vala, Java, Perl,
To know more about:
sudo apt-get install glade
Application -> Programming ->Glade interface designer