Ubuntu is a predominantly desktop-oriented Linux distribution, based on Debian GNU/Linux but with a stronger focus on usability, regular releases, and ease of installation at the expense of platform diversity. Ubuntu is sponsored by Canonical Ltd, owned by South African billionaire entrepreneur Mark Shuttleworth.
The name of the distribution comes from the southern African concept of ubuntu which may be rendered roughly as "humanity toward others", "we are people because of other people", or "I am who I am because of who we all are," though other meanings have been suggested.
The most recent version, Ubuntu 11.04 was released in April 2011. Ubuntu aims to use only free software to provide an up-to-date yet stable operating system for the average user.
Kubuntu and Xubuntu are official subprojects of the Ubuntu project, aiming to bring the KDE and Xfce desktop environments, respectively, to the Ubuntu core. Edubuntu is an official subproject designed for school environments, and should be equally suitable for children to use at home.
Gobuntu is the official subproject, which is aimed at adhering strictly to the Free Software Foundation's Four Freedoms. The newest official subproject is JeOS. Ubuntu JeOS (pronounced "Juice") is an efficient variant of the popular desktop and server operating system, configured specifically for virtual appliances.
Ubuntu releases new versions every six months, and supports those releases for 18 months with daily security fixes and patches to critical bugs. There are also Long Term Support (LTS) releases, which have three years support for the desktop version and five years for the server version. Lucid Lynx (Ubuntu 10.04) is an lts-version.
In the second section you can also find free training material meant for commercial training in Ubuntu but also suitable for self-study