Strictly speaking Linux users do not use an operating system. Linux is the kernel of an operating system. To meet the standards of a modern OS other components have to be added. Boot manager, display manager, desktop environment, window compositor manager, graphical user interface and system utilities. Then add in a default set of applications and we have a Linux distribution.
These software components come from several independent software projects. This means that distributors can change the mix of components to suit their choices. Ubuntu is a Linux distribution based Debian Linux and using the Gnome Desktop Environment and the Unity Graphical User Interface (GUI). Replace the Gnome DE and Unity with the K Desktop environment (KDE) and the Plasma GUI and we have Kubuntu. Use instead the Xfce desktop environment and we have Xubuntu. Use the LXDE and we have Lubuntu.
Razor-qt is not a distro but a desktop environment
http://razor-qt.org/
Manjaro is a Linux distro but based upon Arch Linux
http://manjaro.org/
Antegros is another Linux distro based upon Arch Linux
http://antergos.com/
Regards.
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