Gnome. If you want KDE, you can use Kubuntu, the KDE derivative of Ubuntu.
Ubuntu uses GNOME by default. However, a KDE version is available, named Kubuntu. It doesn't have all the bells and whistles of its GNOME counterpart
Gnome.
Gnome There is a KDE version named Kubuntu, however
Fedora installs the GNOME Desktop Environment by default.
No. There is no single user interface for Linux. GNOME. KDE, Xfce, Fluxbox, and CDE are all examples of user interfaces / desktop environments for Linux.
The most often used X Window (graphical) desktop environments are KDE and GNOME. There are many others.
2
Unix is an operating system that provides a Common User Interface (CUI) for controlling a computer. Thus CUI can run an application that provides a Graphical User Interface (GUI) which makes controlling what the computer does a little easier (e.g. GNOME - The GNU Object Model Environment).
Ubuntu 11.04 has not yet implemented the Gnome 3 interface, but the next version of Ubuntu, 11.10, will use Gnome 3.
Ubuntu - GNOME Kubuntu - KDE Xubuntu - Xfce Puppy Linux - JWM Damn Small Linux - JWM, Fluxbox Fedora - GNOME (default) OpenSUSE - KDE (default) Debian - GNOME, KDE, Xfce Red Hat Enterprise Linux - GNOME Linux Mint - GNOME Xandros - KDE PCLinuxOS - KDE
The shell is used to allow the user to interface with the operating system and run their applications. BASH is a shell, as is GNOME (Often referred to as a "graphical shell."). The kernel, on the other hand, is the core of the operating system. It manages the hardware, resources, and processes running on the sysem.
You can log in via telnet or ssh protocol for a command line prompt environment to Unix, or you can use a graphical user interface such as KDE or Gnome, or the CDE environment via X-windows. In any of these protocols, you must supply a username and password to successfully log into the Unix system.