The Black Orcs or Morannon-Orcs are a breed of hgreater Orcs different from the lager Uruk-Hai.
speculations
Their origin is unknown but they may be identical with the Warrior-Breed or Fighting-Orcs, the Hobgoblins or the larger Orc-Race from Barad-Dûr who fought in the second Age on the Gladden fields.
The Morannon-Orcs could also be identified with the Uruk-lesser Orc halfbreeds known as "Gusmuras" in MERP.
appearance
The Morannon Orcs appear in the Movie Trilogy, The Lord of the Rings Strategy Battle Game and The war of the ring, The Battle for Middle-Earth Series, The Lord of the Rings: Conquest and Tactics and The Lord of the Rings: The Return of the King.Morannon-Orc like breeds also appear in LOTRO.