If you are working with a clean install of Ubuntu and are trying to set up some sort of development environment you will almost definitely need to run sudo apt-get install build-essential.

The command installs the build-essential package which amongst other things installs a C compiler, which you will almost certainly need because a lot of things in the GNU/Linux world are written in C.

Some tutorials will include this step (or bury the build-essential package in with a host of other packages to download) but many of them assume you must have already performed this step.