The types and features of windows used by X11 clients depend on the X11 window manager used during your X Window System sessions.
The anatomy of an X11 window is shown in Figure 14.2.
The topmost portion of an X11 window is called the title bar, and usually contains the name of the X11 client. You can change the name that appears on the title bar by using the X11 Toolkit -title option. For example, to start the rxvt X11 terminal emulator with a custom title bar, enter a command line such as the following:
# rxvt -title "Welcome to Linux! Have a nice day! :-)"