What is Xubuntu?
Xubuntu is the XFCE version of Ubuntu. This means that it uses the XFCE interface as opposed to Gnome. XFCE is the third most popular interface and uses so little resources that it's good for older computers. If looking to install a version of Ubuntu onto a computer that's more than a few years old considering using Xubuntu or an XFCE alternative distribution.
Which version of Xubuntu should you use?
Many times you see a version number after the name like Xubuntu 7.04 or Xubuntu 9.10. The first number is the year it came out like 2007 or 2009. The second number is the month of the year. Generally speaking going with the latest version since it has the most updates and security features.
What type of hardware will Xubuntu run on?
It's made for i386 like your Pentium II, III, IV as well as your AMD type hardware. For the most part it works on most machines. There are some 64 bit versions as well although this might not be necessary for most people.
Some prefer using this distribution on their netbook because it uses fewer resources than Gnome and KDE.
What are some alternative XFCE distributions?
If you load up Xubuntu and do not like it, there are other versions of Linux that use the XFCE interface. Linux Mint XFCE community edition is one to take a look at. It's like Xubuntu but there are differences. If you are currently using Linux, you can always download XFCE and select that as your default session if you wish to switch to it.