What makes a black hole black?
Light can't escape a black hole's gravitational pull.
First off. Let's point out that black holes are not black, but in fact invisible. In order to see something, light must bounce off of or radiate from that something and into your eyes. In this case, that something is a black hole.
Black holes are formed when a star collapses in on itself, squeezing the majority of the star's mass into a tiny space. Too put it into perspective, imagine our solar system's sun squeezed into a box the size of New York. This is why black holes are so dense.
Because black holes are so dense, they have a very strong gravitational pull. So strong in fact that light can't escape its grasp, pulling the light into the center of the black hole. I will include a picture below of an artist's accurate concept of a black hole approved.
A large mass shrink ed to very small volume have very high surface gravity.
Due to very high surface gravity light can not escape from its surface...So we will not be able to see it;. That is why it is called black hole. large mass makes the space curved around.When this reaches a very high limit the light which have the highest velocity can not escape from the event horizon.picture quora.com.