Black holes are and have always been very mysterious. They have even our most gifted physicists scratching their heads about how exactly they work.
They produce unworldly physics that create illusions with light, and even more interesting is that they're just about impossible to see in space without some kind of light bending going on.
Black holes can be formed when large stars die and collapse in on themselves in space. When they explode, it's possible for the gravity to remain after the pressure from the light is no longer there to prevent collapsing.
Black holes have such a dense core that even masses as big as Mount Everest can be smashed down to the size of a grain of sand, as Science Channel explains. Nothing can escape a black hole's gravitational pull; not even light.
They are truly a force to behold.