What is a black hole?

A black hole is a compressed dense mass with an intense gravitational field. The gravitational force of the black hole is so strong that nothing in its surroundings can escape from it, not even light. As a result, the space around a black hole gets distorted. It is similar to a gigantic funnel, which becomes flatter and flatter towards the upper margin. 

Everything near this funnel then slips down and makes the funnel deeper due to its own weight. The
black hole nearest to our solar system is about 8200 light
years away; so there is no real danger of being swallowed
by it.