In days past, before all the electronic, wireless wonders we enjoy today, communication of a situation to the racing driver was done with flags. These 7+ flags are still in use today, from professional road course and oval racing action, down to the autocross and kart racing events.
There is a variety of other flags used, some seem to depend on the series or local conditions. Once again, thanks to the information from the BeaveRun Motorsports Complex is a concise review of what these 8 race flags mean :
Signals the start of a practice or qualifying session or the start or restart of a race. Also signals a clear course.
Slow down, no passing, hold position.
Slow down, no passing, immediate danger, unsafe driving conditions on the track.
The signaled car must go immediately to the Black Flag Station in the pits for consultation.
Black – Open Flag
Signals that you are to enter the pits.
Signals a complete stoppage of driving activity. Come to a controlled stop as quickly as possible at edge of track and within sight of a flag station. Upon indication from a corner worker, proceed cautiously to pits.
Check your mirrors and give consideration to the overtaking car, be prepared to expedite a pass.
Signals completion of the session or the race. Enter the pit at next opportunity.
Signals that an emergency (or slow moving) vehicle is on the track.
Signals you to exercise caution due to a slippery condition or debris on the track