Here's how it works:

* Stars are giant balls of hot gas. These gases exert outward pressure, trying to expand the star.

* Gravity pulls all the matter in the star inwards. This inward pull tries to collapse the star.

* During a star's life, these two forces are in balance. The outward pressure from the star's nuclear fusion reactions counteracts the inward pull of gravity.

* When a star runs out of fuel, nuclear fusion stops. This removes the outward pressure, leaving gravity to dominate.

* Gravity then overwhelms the star's internal structure, causing it to collapse. The collapse can be slow and gradual, or incredibly violent, depending on the star's mass.

This process is responsible for the formation of various stellar remnants:

* White dwarfs: For stars like our Sun, the collapse is stopped by electron degeneracy pressure. This pressure prevents the star from collapsing further, resulting in a dense, compact object.

* Neutron stars: For more massive stars, the collapse continues until protons and electrons combine to form neutrons. This results in an incredibly dense object supported by neutron degeneracy pressure.

* Black holes: For the most massive stars, the collapse is unstoppable and continues until the star becomes infinitely dense, creating a black hole with a gravitational pull so strong that nothing, not even light, can escape.