Expression of disbelief (= when you have just perceived or heard something you can hardly believe). Mostly when an action occurs that could have been avoided.
This expression can be spoken to anyone, however it's mostly used and recommended to be used when being in company of friends who do not necessarily have to be Africans or Afro Americans.
Boy1: Hey! I got 130 dollars. Let's go buy McDonald's!
Boy 2: Really Nigga? You could go buy some Jay's wit dat cash. You need Jay's with dem dusty ass Sketchers