Well depending on transparency and depth buffer it either doesn't matter or really really does....
Also for your confusion it truely is parallel, the best kind in fact. The trivial kind, each pixel's color is independent of every other pixel so you can and thus want too do them ALL at the same time!
Also for your confusion it truely is parallel, the best kind in fact. The trivial kind, each pixel's color is independent of every other pixel so you can and thus want too do them ALL at the same time!