That's one of those things, along with the information referred to in the other parts of this question, that you should really, really know for the final exam.
Light behaves both as a wave and as a massless hunk of energy called a photon.
And light slows down if it's moving through matter. Matter can in principle travel all the way up to the speed of light, but not AT the speed of light. Why we care about blackbodies is that virtually all stars emit light as blackbodies do. The solid iron ball gives off a continuum. The heated thin gas around it is an emission line source.