Is Ubuntu Server an operating system or an add-on for Ubuntu? Also any info on setting up a minecraft craftbukkit server would be nice.
Ubuntu Desktop = linux kernel+GUI (unity) + apps + stuff
For a home minecraft server, which starts and stops at boot and shutdown, you could try this script: http://www.minecraftforum.net/topic/121830-multi-world-linux-minecraft-server-control-script/
For a normal minecraft server, you should use Aleksandar's link:
(I recommend using "screen" either way, with that, you can put anything in the background while you can do other stuff, extremely handy for ssh connections)
About minecraft servers on Ubuntu: My friend told me that minecraft no longer supports ubuntu, but it will work if the server is cracked. Good luck. (editor: i doubt it. a config makes it possible to play "online mode" or "offline mode" nothing to do with ubuntu)
You can download Ubuntu Server from Ubuntu's website and you can also install it as add-on in a ubuntu installation.
I suppose that you want a GUI support for your server, so you should go with the add-on part.
If you want an apache server you will have to install apache.
As for craftbukkit server - link - does not require apache AFAIK.