Does Blender use CPU or GPU ?

I would like to ask you, what Blender uses for rendering. I mean, which one is mainly used (CPU or GPU). Does this information change with changing renderer (I use Yafaray and Blender Render).Thanks for answers.

As far as I know…

Blender internal and most external blender renderers only use CPU.

Exceptions, I think (maybe) that there is a screen render / quick render for blender that uses the openGL view port, which I assume uses openGL and therefore is sorta GPU. Anyone care to correct or expand?
There may be some sort of GPU renderer out there that might talk to blender, but in an unsupported half arsed way - ala Gellato.
Open standards for GPU are still a long way short of production ready.

Ok, thanks.