Supernovae refer to the last stages in a star's life, when it explodes and disappears completely. After this explosion, there are several things that can happen - a black hole may appear or there may be star dust hovering in the universe. Well, this dust, and other materials that came from the massive star that exploded are used to create new planets. Every planet we know of emerged from the dust and particles in the universe - so this means that the same dust coming from supernovae can form new planets as well.
