Purpose: You installed RTM version, and its now not up to date anymore, Aieee! Do something!
Let me begin by pointing out the obvious here: you do not need this update because of all the new features it gives, you need this update because of all the bug fixes it does! My god, that almost rhymed, I could start writing poetry. The post is divided into two parts: the first part containing the requirements that you need to do before you can move to the second part, which is the actual installation of the update. Do not step over the first part, you really do need to do all of these.
Bug fixes in Configuration Manager 2012 SP1
New features in Configuration Manager 2012 SP1 (Referenced)