What is the final stage of stellar evolution?

Answer 1

Supernovae are caused by the gravitational collapse of massive stars. When the material in the core of the star reaches the density of an atomic nucleus, nuclear forces (actually "neutron degeneracy pressure," but that's a whole new topic) balance gravity and the collapse is suddenly halted. This creates a shock front between the material that has stopped and the material that is still falling inward. The shock front moves moves outwards (only direction it can go, think about it) through the star and explodes as a supernova.

So, to answer your actual question, that small dense remnant is called a neutron star. If the neutron star can steal some material from somewhere (either another star or perhaps the remains of its parent star), it might become so big that gravity becomes dominant again, and will collapse, this time into a black hole.