Unity is a shell interface for the GNOME desktop environment developed by Canonical for its Ubuntu operating system. Unity debuted in the netbook edition of Ubuntu 10.10. It is designed to make more efficient use of space given the limited screen size of netbooks, including, for example, a vertical application switcher called the launcher. Unlike GNOME, KDE Software Compilation, or Xfce, Unity is not a collection of applications but designed to be used with existing GTK+ programs.
Ubuntu has traditionally used the full GNOME desktop environment; founder Mark Shuttleworth cited philosophical differences with the GNOME team over the user experience to explain why Ubuntu would use Unity as the default desktop instead of GNOME Shell, beginning April 2011, with Ubuntu Natty Narwhal (11.04).
Continue Reading... Ubuntu has traditionally used the full GNOME desktop environment; founder Mark Shuttleworth cited philosophical differences with the GNOME team over the user experience to explain why Ubuntu would use Unity as the default desktop instead of GNOME Shell, beginning April 2011, with Ubuntu Natty Narwhal (11.04).
source:http://linuxpoison.blogspot.com/2011/06/135781677510263.html