I always forget how to find out, which version of the distribution I am using: here's the answer !
From the command line,
lsb_release -a will print the distribution name as well as version number and
uname -a the Kernel number.
In Gnome, you may get the information, going to
System ==> About Ubuntu (this documentation will display the distribution version number).
Hard Info is a nice little utility tool, that will display plenty of useful information about you box, including the above.