The GNOME Project was started in 1999, to provide a Free and open Source DE. Although KDE was already FOSS, it used the non-free Qt widget framework (until version 2). GNOME chose to use the GPL licensed GTK+ framework for its environment. It was also meant to provide a simpler and cleaner interface than KDE.
The first GNOME environment looked a lot like windows 95. When GNOME 2 came out, there was a major redesign of everything: the system panel moved to the top of the screen (where it still resides), the new Window Manager provided a distinctive look and feel, which, in the opinion of KDE users looked exactly as the name implied: gnomeish. Gnome also seemed to over-simplify things, where you’d either accept the default options or go through a painful process of manually changing settings if you wanted to customise your own desktop. (This has later been addressed by several graphical tools, but never to the extent KDE provided out of the box.)
When GNOME 3 came out, it had a similar effect on users than KDE4 did: It turned off many GNOME fans, who sought refuge in different environments and forks of the GNOME2 desktop. Gnome 3 was not only a major redesign of the user interface, it completely changed the user experience, and work-flow as well. With touch-screens in mind, albeit in an era when no touch-screen devices ran GNOME (They still don’t), the DE became the bastard child of a PC desktop and a non-existent tablet OS.
Despite its initial weirdness, GNOME 3 is actually quite enjoyable and usable, although it might need some tweaking. The main problem, as always, seem to be people’s habits: They don't want to learn anything new, and when something comes and changes the way they do things, they tend to frown. This is of course quite understandable, but a bit of open-mindedness goes a long way: once you’ve got used to using GNOME3, it can even improve your work experience. (More valid criticism of GNOME 3 like its infamous
systemd dependencies, is out of the scope of this document.)
Debian comes with a relatively recent version of GNOME3, so you can enjoy most of its benefits.
There are two noteworthy GNOME derivatives, MATE and Cinnamon, each forking a different version of GNOME and offering a different desktop experience, sharing the frustration with the changes in GNOME 3, come 2011.
There was quite a bit of controversy around GNOME 3 (or the “GNOME Shell”, as the new user interface was dubbed), and many GNOME enthusiasts did not quite feel all right in their new gnome-home. The two projects, MATE and Cinnamon emerged roughly about the same time. MATE continued development of GNOME 2, keeping the tried and trusted interface and controls while continuing to provide support for new functionality. The project is quite popular with former GNOME 2 users.
Cinnamon started as a fork of the new GNOME shell, using the new GTK3 toolkit, but later grew into its own DE. Cinnamon is developed by (and initially for) Linux Mint, offering a more traditional desktop, that uses newer technology than MATE.
Both Desktops are available in Debian as well and can be installed as the default DE.