As members or flavors of the Ubuntu family of Linux operating systems, Ubuntu, Kubuntu and Xubuntu share the same project servers, development infrastructure and software repositories. Each can install and run software designed for all other flavors. In addition, all three flavors benefit from efforts by Ubuntu's parent, Canonical, to produce a Linux distribution that is easy to install, supports modern PC hardware and simplifies access to the software needed to play popular video and audio file formats.
Ubuntu, Kubuntu, and Xubuntu each use a different desktop environment to control the way their applications look and function as well as the way you access resources on your system or over a network. Ubuntu uses Unity, a recent fork or feature redesign of the Gnome desktop. Kubuntu, on the other hand, uses the KDE Plasma desktop, while Xubuntu has Xfce as its desktop environment. The Unity desktop is designed to provide a common user experience on Ubuntu users on PCs as well as smartphones, tablets and set-top boxes. Both KDE and Xfce, however use a familiar PC desktop metaphor that users of Windows 7 will recognize.
To install and run Ubuntu or Kubuntu, you need a 700 MHz or faster 32-bit Intel processor, at least 512MB of RAM, a minimum of 5GB disk or SSD space, and a 1024 by 768 pixel display. In addition, Unity requires an OpenGL 1.4 or higher-compatible video card with 3D hardware acceleration and at least 256MB video RAM. You need 256MB of system memory and 6.1GB free disk space to install Xubuntu's XFCE desktop. Nonetheless, Xubuntu's developers recommend you have at least 512MB RAM installed to run the desktop. Each Ubuntu flavor, however, runs better with more RAM and a faster single or multi-core processor.
Default Programs Included
Each distribution ships with a selection of applications which distinguishes it from other Ubuntu desktops. For example, Xubuntu uses Risetto to view and organize photos, while Kubuntu and Ubuntu use Gwenview and Shotwell, respectively. Ubuntu and Kubuntu both ship with the LibreOffice Writer word processor, while Xubuntu comes standard with Abiword. You can listen to music files on Xubuntu with the Gmusicbrowser or Parole audio players. Amarok is the default music player for Kubuntu, while Ubuntu uses Rhythmbox. In addition, each desktop uses different tools to perform system tasks like adding or removing software, managing files or controlling system settings. For instance, Ubuntu uses the Nautilus-based Files, Kubuntu uses Dolphin and Xubuntu uses the Gigolo file manager.
There is no task you can do with Ubuntu that can't be done with either Kubuntu or Xubuntu. Nevertheless, each desktop has a target audience. Ubuntu targets users who want a modern desktop that is easy to use, complete with the tools you need to work or play, and has a user interface that resembles a smartphone or tablet device. Users who value the ability to customize their system to their hearts content may prefer Kubuntu. Xubuntu, on the other hand, targets users who want a simple, more conventional Windows-like desktop that is not too resource-heavy on new PCs and runs well on older, slower, less-powerful hardware as well.