The life cycle of a high mass star starts with a Stellar Nebula. From there the high mass star goes into its main sequence stage where it begins nuclear fusion with hydrogen and helium.
After a while the nuclear fusion finishes and gravity begins to take over the star. The star begins to expand and die losing its heat but growing very large. It is now a Red Super Giant.
This is a super nova. It is what happens when the core of a Red Super Giant collapses on itself and forms a massive explosion. The outer layers are blown off from this explosion. From here the remaining bits will become a neutron star. The largest stars gravity will pull everything in and create a black hole.