From LQWiki
Ubuntu is a Debian-based distribution. A number of Ubuntu flavors are available in addition to the gnome-based default. These include: kubuntu (kde-based), xubuntu (XFCE4-based), edubuntu (aimed at classroom use), and a number of others.
The unofficial Ubuntu Guide
There is a wealth of information here for the use, administration, and maintenance of Ubuntu.
Installing software
To install software, use the Gui Synaptic or the cli apt-get. Example:
apt-get install firefox
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