A black gap in traditional theory is characterized by having "no hair," that is, it is so simple that it can be totally described by just three parameters, or its mass,its spin, and its electric charge. Even though it may have formed out of a complex mix of matter and energy, and all the specific details are lost when it collapses to a singular point. This is surrounded by a "horizon," and once anything – matter or light (energy) – falls within that horizon, it cannot escape. Hence, and the singularity appears black. Outside this horizon a rotating,accreting disk can radiate freely.
Source: phys.org