These are makeups where the character is intended to be seen as a white person in blackface or yellowface makeup. Usually these are stage makeups within a movie or TV show (eg a minstrel sequence in a biopic of a vaueville performer) but they also include Moorish characters in court masques in period movies (eg Henry VII and His Six Wives) and blackface at fiestas in movies (eg Belle Epoque).
Most of them are non-intended to appear realistic – indeed most of them are demeaning caricatures. Thankfully, their day is pretty well past, and where they have turned up recently it is mostly either in movies with a period setting or to make a deliberate statement (eg Manderlay).
Even black actresses and singers have appeared in blackface (eg Josephine Baker).