Magical Negro
tl;dr: Closer to Earth ethereal Black character existing only to help the White hero.
Long definition:
"Friendly black optimistic advice"
— A Trailer For Every Academy Award Winning Movie Ever
In order to show the world that minority characters are not bad people, one will step forward to help a "normal" person, with their pure heart and folksy wisdom. They are usually black and/or poor, but may come from another oppressed minority. They step (often clad in a clean, white suit) into the life of the much more privileged (and, in particular, almost always white) central character and, in some way, enrich that central character's life. If the Magical Negro (also known as Magic Negro or Mystical Negro) is from a society of Noble Savages, expect an Anvilicious Aesop about the failings of the protagonist's society — which usually leads to the protagonist "Going Native".
With such deep spiritual wisdom (and sometimes — though not always — actual supernatural powers), you might wonder why the Magical Negro doesn't step up and save the day himself. This will never happen. So enlightened and selfless is he that he has no desire to gain glory for himself; he only wants to help those who need guidance...which just happens to mean those who are traditionally viewed by Hollywood as better suited for protagonist roles, not, say, his own oppressed people. In fact, the Magical Negro really seems to have no goal in life other than helping white people achieve their fullest potential; he may even be ditched or killed outright once he's served that purpose. If he does express any selfish desires, it will only be in the context of helping the white protagonists realize their own racism and thereby become better people.
http://tvtropes.org/pmwiki/pmwiki.php/Main/MagicalNegro
