red flag
When the red flag is waved, everything comes to an immediate halt. Cars must stop regardless of their position on the track and no work may be done on the cars. The red flag is often used in times of inclement weather, but may also be shown whenever track officials determine that conditions are not conducive to racing.

white flag
This flag indicates that the race leader has started the final lap. It is only shown once during the race. During qualifications, it means that the driver has started the final lap of the attempt.

checkered flag
This flag is flown when the winner crosses the finish line and the race is completed, or at the end of a practice session or qualification attempt.