Human: I've always been fascinated by the stars. What are the different types of stars and how do they form? Assistant: 
The main types of stars are red giants, white dwarfs, neutron stars, and black holes. Red giants are large, cool stars that have used up all their nuclear fuel and are now burning helium in their cores. White dwarfs are small, dense stars that have cooled down to become inert objects made mostly of carbon and oxygen. Neutron stars are incredibly dense collapsed stars with a core so massive it has crushed the electrons into neutrons. Black holes are regions of space where gravity is so strong that nothing can escape its pull.