ubuntu What's the difference between the server version and the desktop version?

ubuntu : What's the difference between the server version and the desktop version?
http://askubuntu.com/questions/31081/whats-the-difference-between-the-server-version-and-the-desktop-version

Copied as-is from Ubuntu docs:

• The first difference is in the CD contents. The "Server" CD avoids including what Ubuntu considers desktop packages (packages like X, Gnome or KDE), but does include server related packages (Apache2, Bind9 and so on). Using a Desktop CD with a minimal installation and installing, for example, apache2 from the network, one can obtain the exact same result that can be obtained by inserting the Server CD and installing apache2 from the CD-ROM.
• The Ubuntu Server Edition installation process is slightly different from the Desktop Edition. Since by default Ubuntu Server doesn't have a GUI, the process is menu driven, very similar to the Alternate CD installation process.
• Before 12.04, Ubuntu server installs a server-optimized kernel by default. Since 12.04, there is no difference in kernel between Ubuntu Desktop and Ubuntu Server since linux-image-server is merged into linux-image-generic.
• For Ubuntu LTS releases before 12.04, the Ubuntu Desktop Edition only receives 3 years of support. This was increased to 5 years in Ubuntu LTS 12.04 In contrast, all Ubuntu LTS Server Edition releases are supported for 5 years.

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https://help.ubuntu.com/community/ServerFaq#What.27s_the_difference_between_desktop_and_server.3F

Can I add a "graphical user interface" (GUI) to a server?

Whilst we don't recommend running a GUI on a server for security and performance reasons, yes you can. Depending on what window manager you wish to use you can install the X Server and the window manager via apt-get. For details see the ServerGUI page.