I have the Ubuntu 12.04 Desktop freshly installed. If i execute the following command, what exactly happens?
sudo apt-get install gnome
And what is the difference between the above command and installing gnome-shell or gnome-session-fallback?
I would like to expand on Uri Herrera above answer .
What is Gnome ?
It is basically a meta package consisting Both gnome-shell and gnome-fallback session.
GNOME Shell uses Mutter, a compositing window manager based on the Metacity window manager, and the Clutter toolkit to provide visual effects and hardware acceleration. According to GNOME Shell maintainer Owen Taylor, it is set up as a Mutter plugin largely written in Javascript.
From Gnome official page
Gnome-shell provides core interface functions like switching to
windows and launching applications. GNOME Shell takes advantage of the
capabilities of modern graphics hardware and introduces innovative
user interface concepts to provide a delightful and easy to use
experience.
You can refer the technology behind GNOME Shell page.
If your computer's graphics card doesn't support certain features, a more basic version of the desktop will be displayed and you will see
a message telling you what happened. This is called fallback mode,
and it allows you to use GNOME on your computer without some of its
more advanced features..
..Starting in fallback mode doesn't necessarily mean that your
graphics card isn't good enough to run GNOME - it might just mean
that you don't have the right drivers installed for your graphics
card. If you can find better graphics card drivers for your computer,
you may be able to run the full version of GNOME.
Basically it is for Unsupported Graphic Cards
