Black Hole

A black hole is the result of a very massive star that dies. Gravity will crush the star into a tiny point known as a singularity. A singularity is thought to hold no space at all.

Black holes usually start out small, as they swallow matter around them, the event horizon will become larger. All matter that enters a black hole will end up in the singularity. The event horizon is the point of no escape of the black hole. Not all matter will get sucked into the black hole, most of the matter just orbits the black hole, this matter the orbits the black hole is called the accretion disk.

Hawking Radiation
Since black holes swallow matter, it will start to take energy away from itself. This process is extremely slow. It will take up to a googol years for a supermassive black hole to evaporate. When it completely evaporates, it will burst out tons of energy. Though nobody would be there to see it, since the sun would end humanity in another 4.5 billion years.