Explanation:
Black holes are the most massive and dense objects in the whole universe. They are peculiar objects. The gravity near black hole is so strong that even light can not escape it. That is why the name: Black hole. It is formed after the death of a supermassive star. All the mass of the star is condensed in to a very small area having a very string gravity. Imagine the Sun squeezed in to an object of diameter of just 3 km!
You can define it as a dead super massive star from which nothing can escape.
