what exactly do you mean by black hole?

A black hole is a perticular spot where the maximu light is absorbd and not reflected back.

black hole is the equivalent of a water draining hole in a swiming pool from which the stopper has been pulled. it sucks down everything in its path.. everything sinks to the middle of it and we still dont know where all that matter goes and what happens to it. but we know that the gravity in a black hole is so strong that even light cannot escape it or say even light sinks into it. so we cannot see a black hole because if no light can escape it then it would be black. and space itself is black so we cannot see black hole over a black space.. we only see it when something like a star is being sucked into it . that time we see the star vanishing and the black hole gives itself away.

A black hole is an object in space with a powerful gravitational pull that even light cannot escape .If something gets trapped in a black hole then escape from it is really impossible.