A desktop environment is a GUI for an Operating System that not only decides how the interface looks to the user, but also how applications interact with the user. It usually consists of a window manager (e.g. Metacity) and a widget toolkit and then displays what the user should see, along with a file manager (e.g. Nautilus) and also few programs and libraries corresponding to the environment. Examples of Desktop environments are Aqua in Macs, Aero in Win7 etc. Common Desktop Environments of Linux are GNOME and KDE. They’re both free and open source. Lets cover them up one by one.
GNOME- It is one of the most popular desktop environments. It is an abbreviation of GNU Network Object Model Environment Launched in 1997, it uses the open source GTK+ widget toolkit. One of the most important reasons for its success is the GNOME development platform, an extensive framework for building applications that integrate into the rest of the desktop. The latest version of the project is GNOME 3.0 launched in 2011.
Many OSes still use GNOME 2 as the default environment, as it is very stable and mature. GNOME 3 has more eye candy. GNOME is the default desktop environment on many operating systems like Ubuntu, Fedora, Linux Mint and also some non Linux projects like OpenSolaris.
KDE – The other very popular desktop environment, KDE is one of the oldest desktop environments, even older than GNOME. KDE is known for the eye candy it offers. It uses Qt as the software core. Thus, it is easier to port KDE software to other OSes. KDE has higher memory requirements than GNOME, but it runs better and faster than GNOME on new systems.
Dolphin is the default file manager for KDE. KDE has more applications written for it, because Qt applications look better and are easier to be made cross platform. The latest version of KDE is 4.7, and the screenshot below displays KDE 4.6. KDE is used in Kubuntu, OpenSUSE, BSD etc.
Other Desktop Environments
Xfce– It is a desktop environment focused on speed and eye candy with minimal memory usage. Xfce is also based on GTK+ toolkit. The Window manager used is Xfwm. The main feature of Xfce is its low memory requirements. I tested it on a virtual machine with 64Mb RAM with KateOS and it ran fine!
Xfce has its latest version at 4.8, which is used in many distributions. Most Linux distributions have a separate Xfce version. e.g. Xubuntu, Linux Mint Xfce etc.
LXDE– Lightweight X11 Desktop Environment is meant to be used on very old PCs. LXDE has enough guts ti run on 32Mb RAM, which few other can do. It is also quite visually pleasing.
LXDE is used in distros for old systems. The base versions of many distributions have LXDE, for example Knoppix. This is done so as to fit it into a liveCD.
GNOME vs KDE
KDE has a reputation for having confusing menus and options. GNOME is better for the new user. Both KDE and GNOME can be customized to behave exactly the way you want. What desktop you prefer is your own choice and preference. GNOME applications can be used in KDE and vice versa, but more applications are supported out of the box by KDE. KDE is more pleasing to look at but GNOME is not bad either! My decision has to be diplomatic, no need to fight! Choose according to the distribution. No one can tell which is better. For the new user, I say, go for GNOME!