What does the black flag mean?

Foul. In car racing, the referee's black flag means that the driver who has been warned has misbehaved or fouled on the track and must return to the pit immediately after completing a lap. This sign will show the car number at the start and end. There are red flags, white flags, black flags and green flags in the race. The red flag indicates the start or end of the race, the white flag indicates the need to drive slowly, and the green flag indicates that the track has been repaired and drivers can resume normal speed and track.