Linux X Window,KDE,GNOME

X Window System [X11] 
X Server, X Client

Implementation of X11::
X.Org Server [XOrg]  [ X.Org Foundation Open Source Public Implementation of X11 ]

XFree86 ,the freely redistributable open-source implementation of the X Window System continuously since 1992.

"X is primarily a protocol and graphics primitives definition and it deliberately contains no specification for application user interface design,
such as button, menu, or window title bar styles. Instead, application software – such as window managers, GUI widget toolkits and desktop environments,
or application-specific graphical user interfaces – define and provide such details. As a result,
there is no typical X interface and several desktop environments have been popular among users."

X Client::Desktop Environments:: KDE、GNOME、XFCE、LXDE ......

GNOME vs KDE:

KDE[Kool Desktop Environment] QT C++
GNOME[The GNU Network Object Model Environment]  GTK+ ,C not C++    RedHat、Novell

Enlightenment vs GNOME
"Enlightenment is a window manager for Unix-like operating systems. GNOME is a desktop environment which includes a window manager.
GNOME is a fully featured desktop environment which includes many applications users may require on a daily basis. "

GTK vs Qt

wxWidgets

wxWidgets is a C++ library that lets developers create applications for Windows, OS X, Linux and UNIX on 32-bit and 64-bit architectures as well as
several mobile platforms including Windows Mobile, iPhone SDK and embedded GTK+.
It has popular language bindings for Python, Perl, Ruby and many other languages.
Unlike other cross-platform toolkits, wxWidgets gives its applications a truly native look and feel because it uses the platform's native API rather than emulating the GUI.
It's also extensive, free, open-source and mature.

Chrome Browser & Chrome OS   Google