What is a black hole?

You ask: What black hole?

Take mountain. Squeeze mountain small as berry. Squeeze more, small as dust speck. When very big star die, star fall into itself like that. Now gravity pull so strong, nothing escape — not rock, not spear, not even light. That why hole look black: light fall in, no light come back out. Edge of no-return called event horizon. One step past edge, no coming home to cave, ever. Cave wisdom: black hole not hole. Black hole is most stuffed thing in whole sky.