A nova is a stellar outburst but on a less violent scale than a supernova. Unlike a supernova, a nova does not destroy the star.
Novae occur in binary systems where one of the pair of stars is a hot, compact object called a white-dwarf. The other star in the system (maybe a main sequence or red giant star) orbits close enough for material to drawn into an accretion disk around the white dwarf. The material (hydrogen and helium mostly) adds mass to the surface of the white dwarf and increases the temperature and pressure until a runaway nuclear reaction begins. Some of the energy released is in the form of light (the nova in this case brightened by 25,000 times than the progenitor binary system) and intense stellar winds - strong enough to blow away the deposited material so that the reaction eventually grinds to a halt. The flare in brightness is followed by a decay to normality.
The nature of the binary system means that the process may repeat after intervals of decades, centuries or many millennia.
Novae can recur if we wait long enough.
Finding the nova
Right Ascension 20h 23m 30.1s
Declination: +20° 46' 04"