What does black in white mean in gay porn?

What is black in white?

An active Black Male engaging in penetrative sex, with a white person. This is where the active or top is Black, the bottom or submissive is White.

White in Black is the reverse, in which the White partner is the dominant one, or the top, and the Black partner is the bottom, or submissive.

Black in White can refer to where both are males, or the white partner being female.