Novas are relatively small explosions in double star systems. They come about when a white dwarf’s intense gravity tugs material away from a companion star. Gas piles up around the white dwarf and eventually becomes dense enough to ignite in a burst of nuclear fusion.
Most supernovas, meanwhile, mark the deaths of massive stars and the formation of neutron stars. They are triggered when a shockwave tears through the outer layers of a dying star, igniting a firestorm of nuclear fusion.
Finally, hypernovas are ultra-energetic supernovas marking the birth of black holes and associated with the release of intense gamma-ray bursts.