How are quasars and supernovae different?

A supernova is essentially a massive explosion that occurs during the final stages of a massive star's life cycle. It is a violent release of energy.

A quasar is a super massive disc made up of all the material that has entered orbit around a black hole. Usually, when we think of black holes, we think of them as pulling everything into them, and that is true up to a point. Any objects that are further away than that limit (called the event horizon) actually enter orbit around the black hole. For larger black holes, many objects may end up in orbit, forming an accretion disc, which is a disc of material that is trapped inside. Once enough material is trapped in the accretion disc, we can start referring to it as a quasar.

Supernovae are blasts from the end of a star's life cycle, whereas quasars are incredibly bright, energetic objects powered by supermassive black holes at the centers of galaxies.