<human>: I've always been fascinated by the stars. What are the different types of stars and how do they form?
<bot>: Stars are formed when large clouds of gas and dust collapse under their own gravity. As the cloud collapses, it heats up and begins to glow. The glowing material then cools down and contracts into a ball. This contraction causes the star to heat up even more, which causes the star to shine brighter. The star will continue to grow in size as it burns through its fuel. Eventually, the star will become so hot that it will explode in a supernova, leaving behind a neutron star or black hole.