During the collapse it can happen that the outer envelope of the star collides with the inner neutron core, which sets up shock wave that results in the outer layer of the star exploding. This results in a supernova, a spectacular event seen occasionally here on Earth (the last one was in 1987). In such a collision, iron nuclei can absorb neutrons to form heavier elements such as Uranium. This means of producing and releasing heavy elements into the cosmos is the primary way that planets such as the Earth contain these elements - in a very real sense, the Earth is a product of some supernova explosions that happened billions of years ago.
The remaining neutron core left after a supernova explosion forms the neutron star. This core typically is rotating rapidly, and together with the strong magnetic fields that are present, can create what we call a pulsar. A pulsar is a neutron star that emits radio waves at regular intervals, which are the result of fast moving particles being accelerated by the intense magnetic fields present.