Discover the version of Ubuntu you are working on

Normally you know which version of a given distro you are running if you are on your machine, but what if you are on a rented server, or a friend's machine.

If you want to know which version of Debian or Ubuntu you are running, you can always check the /etc/apt/sources.list there you will see the version you are running but a better way is to run this on a terminal: