What is it?
Ubuntu without Unity, it uses GNOME Shell.
This is a free and open source operating system based on the popular Ubuntu system, but with a pure GNOME interface. Versions of Ubuntu from 11.10 and on will not ship the classic Gnome interface, opting instead for the Unity interface that is disliked by many. This project is based almost entirely on the regular Ubuntu OS, with just several changes to the interface.
It is an Ubuntu based distribution.
You can get it from their site.
Download and Install as usual.