A black hole is defined as a region of space-time, which has an intense gravitational field such that no matter or radiation can escape.
A black hole is a place where matter has collapsed in on itself. It is the final stage of a massive star which has undergone a supernova explosion.
This catastrophic collapse results in a huge amount of mass being squeezed in an incredibly tiny volume. The gravitational effect of this place is so great that nothing – not even any particle or light – can escape from inside it.
Because no light can get out, black holes are invisible.
