the is inside a black hole or what is a black hole
A black hole is a place in space where gravity pulls so much that even light can not get out. The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying.
Because no light can get out, people can't see black holes. They are invisible. Space telescopes with special tools can help find black holes. The special tools can see how stars that are very close to black holes act differently than other stars.
A black hole has a boundary, known as the event horizon. This is the point where the escape velocity is more than the speed of light. The gravity is just strong enough to prevent even light from escaping. Because nothing can travel faster than light, everything else will get dragged back also.