A black hole is defined as "a region of space having a gravitational field so intense that no matter or radiation can escape". 

You could also call it a hole that swallows everything in its way (with a few restrictions of course).

Now, let's start from the beginning... How does a black hole form?

Well, a black hole forms or is created when a massive star dies or implodes and dies by simply disappearing over a lot of time (about a googol).

The Sun is too small to become a black hole, and instead when it dies it will become a white dwarf.

You might be wondering that since a black hole swallows LIGHT then could it swallow an entire galaxy or even planet Earth?