Formula One uses a system of colored flags, both physically displayed at marshal posts and shown digitally on dashboard panels inside the car, to communicate track conditions instantly to every driver on circuit. Understanding this system explains a lot of what happens during a race that might otherwise seem confusing to a new viewer.
Yellow Flags
A yellow flag warns of a hazard ahead, such as a stopped car or debris on track, and requires drivers to slow down and refrain from overtaking in that section until they pass the danger. A double yellow flag signals a more serious hazard, requiring drivers to be prepared to change direction or stop completely if necessary.
Red Flags
A red flag stops the session entirely, typically used after a serious accident, extremely poor visibility, or a track blockage that cannot be safely driven past. All cars must return slowly and carefully to the pit lane, and the session may later resume from a standing or rolling restart depending on the circumstances.
Blue Flags
A blue flag is shown to a driver who is about to be lapped, indicating that a faster car is approaching from behind and should be allowed to pass at the next reasonable opportunity. Ignoring repeated blue flags can result in a penalty, since blocking a faster car unfairly affects the race for those ahead.
The Chequered Flag
The chequered flag signals the end of a session, most famously the finish of the race itself. It remains one of the most recognizable symbols in all of motorsport, marking the definitive end of competition for that event.
Other Signals
Additional flags cover specific situations: a green flag signals that a hazard has cleared and normal racing may resume, a black-and-white flag warns a driver about unsportsmanlike conduct, and a black flag with an orange circle indicates a mechanical problem the driver must address by returning to the pits.