Could somebody please explain what a PHD actually is?

[MattDillonsPants]

I know what a PHD is in one way but not in another. I understand that it's further, deeper study...but that's all.

It's a piece of original research that takes, usually, 3 years' full time work, and is basically intended to give the student the skills needed to become a fully fledged independent academic researcher in that discipline. So it is meant to actually contribute to new knowledge somehow, but also is supervised by (hopefully) people who will help the fledgling researcher develop the skills they need to function independently in the future. The key thing about it is that it is primarily research based rather than taught. You have to have an undergraduate degree first, and very often/usually (depending on the discipline) a relevant Master's. This is so that you have enough knowledge at a high enough level to have a fighting chance of surviving.