The ability to run a GUI is commonly called X11 with different implementations. The most popular in the Linux world is called X.Org Server. There are several but the most popular it seems are Gnome, KDE, and Xfce.
GNOME,KDE
no
The GUI uses unnecessary resources.
Yes and no. Yes, Linux has a GUI. Dozens, in fact, all running on the X Windowing System. No, Linux is not BASED on a GUI. Only Windows really has the concept of an operating system "based" on a GUI. To Linux, the X Windowing System and whatever you run on top of it is just another application.
Not sure what your question is asking, other than the GUI is displayed by the desktop manager.
cd ls
Windows has a GUI and CLI. You use the GUI pretty much all the time. Dump the windows and get a Linux install, try ubuntu and get used to using the well structured CLI. The GUI will make more sense then in general.
The GNU C Compiler (GCC).
Yes
X Windows
gnome and kde
The Linux kernel itself does not include a GUI. However, most Linux distributions have one. Yes, Linux have a GUI.Today many kind of vendor available in Linux Like Redhat fedora,Ubuntu,Suse, Mandriva and many more. Those Linux version provide Cmd and GUI mode for work.
Multimedia has the same purpose in Linux as it does in Windows or Mac OS X. Multimedia is commonly used for entertainment, but also for educational / instructional purposes.