Ubuntu is a Debian-based LinuxDistribution. It is developed by Canonical, a company founded by South African philanthropist Mark Shuttleworth, who made a lot of money off Thawte. According to its site,
One of Ubuntu's main strengths is bringing a nice up to date DesktopEnvironment (each GNOME release is followed closely by an Ubuntu release) to the architecture and package breadth of Debian. Ubuntu is also committed to a 6 month release cycle, with 18 months of security and dataloss upgrades. While still a very young LinuxDistribution in the scheme of things it has a lot of potential and has very quickly become one of the most popular and successful Linux distributions. Because of this, WLUG have adopted is as their official supported distribution for the 2005 Installfest.
See also UbuntuNotes.