When most stars die, they slowly degrade into duller forms called white dwarves. It’s hard to say how many white dwarves are out there, and it’s widely agreed that the census bureau should get to work on that. When a star is not big enough to become a white dwarf or a black hole, it explodes in a sort of cosmic hissy fit. These explosions, called supernovas, started to happen billions of years ago, and are responsible for creating the atoms in everything, even your food. Scientists believe this is why avocados go bad so quickly.
Conversely, black holes are born when a star collapses into itself, becoming smaller and denser until it becomes a single point with no radius, infinite density, and rent is still $2000 a month. This tiny point is called the singularity, and nothing can escape its gravitational pull – and it will probably remain a singularity until it stops being so needy.
The point at which light cannot escape a black hole’s gravity is called the event horizon, formerly known as One Toke over the Line. We can’t know what lies beyond the event horizon, because anything crossing it cannot report back to us. This feature is the reason why scientists call black holes “the universe’s non-disclosure agreement”.