What is a true black belt?

Answer 1

In many of the oldest traditions in the Martial Arts, a black belt was the result of years and years of training, such that the white belt eventually became black. In these traditions, it is improper to wash or launder the belt, as it served as a sign of respect to the art itself (or for other reasons). A "brown belt" was an experienced martial artist whose belt wasn't quite black.

Answer 2

A black belt certificate is like an accomplishment. It is similar to a diploma. It is something with proves that you have reached the top in this field. Of course, like any other diploma, it does give you the right to teach and pass on what you have learned.