Flags and their meanings will be covered at the driver's meeting each day. But if you want to study in advance, here are the typical flags you are likely to see, and what they mean:
Green Flag: Track is open. Under green flag, passing is allowed in designated passing zones only, and with acknowledgement from the driver being passed. Green flag is shown only at start finish and is often omitted during DE events, and the track is considered Green unless the yellow or other flag is shown.
Yellow Flag: Used as a warning flag for danger or an obstruction ahead. Stationary: Danger ahead, No Passing (even in passing zones). Be in full control and prepared to drive alternate lines and, proceed with caution. This flag is given at one or more location for a localized obstruction either as a standing yellow for minor hazards or typically as a waving yellow flag for serious hazard potential. You may see a standing yellow providing advanced warning at a station before a station displaying a Waving Yellow Flag. Your car should be fully and completely under control in a yellow flag zone.
When two yellow flags are displayed at any station (typically as a two stationary yellow flags), then this indicates a full course Yellow. When the "double yellow" flags are in effect, you should slow down, and proceed with caution. No passing is allowed anywhere on the track (even in passing zones) under Double yellow flag condition. In Race settings this condition will usually indicate a pace car is entering the track for a grouped restart. In DE settings you should consider that there might be course workers and emergency equipment elsewhere on the track. Your car should be fully and completely under control in a yellow flag zone.
White Flag: Emergency, service, or slow moving vehicle is on the course. Under a white flag, passing is prudent only when full visibility of the track section in which the pass will occur is possible.
When a stationary yellow and black flags are displayed at any station, then this indicates a full course Yellow and a "Black All". When the two "yellow/black" flags are in effect, you should slow down, and proceed with caution to the track exit and enter the hot pits. No passing is allowed anywhere on the track (even in passing zones) under yellow/black flag conditions. You should consider that there might be course workers and emergency equipment elsewhere on the track.
Checkered Flag: Session is over. When the checkered flag is out, you can complete one cool down lap, and proceed into the pits. The cool down lap should be driven at lower speed, and no passing is allowed, even in passing zone under checkered flag conditions. As you pass each corner stations, acknowledge their efforts and let them know you have seen the flag with a brief wave.
Black Flag: A black flag can be pointed at a particular car by the corner worker, or can be a general or standing black flag at all stations for all cars on the track. When the black flag is displayed to a specific vehicle, that vehicle must enter the hot pit area and see the grid master for instructions. The Chief Instructor will explain the reason for the black flag. A standing black flag at all stations (Black-All) indicates all cars should exit the track to the hot pits. Often shown with a stationary yellow as described above. Typically the first car to receive the checker will also receive a standing "Black-All" which will precede that first car around the course.
Red Flag: A red flag indicates danger on the track. All cars must stop as soon as safely possible. When stopping on red flag condition, you should pull off line but remain stopped on the pavement and secured in your car until given instructions by a corner worker. Do not go off the pavement as you could bring dirt or mud onto the track when it is time to proceed. Also, hot catalytic converters sometimes cause fires if they come into prolonged contact with dry brush or grass. If you have not stopped on a level place, please turn your motor off and place your car in gear. Holding your car stopped with the handbrake or footbrake on a slope will likely warp your brake rotors.
Blue with Yellow Stripe: The blue flag with the diagonal stripe is used to signal a driver that his vehicle is impeding faster traffic. The car at which this flag is waved is being notified to allow faster traffic to pass at the next passing zone. For this reason, some call this the "move over" flag. Others call it the "Check your mirrors" flag.
Black-Orange Disk (Meatball) Mechanical Flag: A mechanical or "meatball" flag is waved and pointed at a particular car by the corner worker to indicate a mechanical issue exists with the car. That vehicle must reduce speed and enter the hot pit area and see the Black Flag Steward for instructions and assistance.
Surface Flag: Used as a warning flag for something on the track surface. This could be debris, dirt, gravel, a part fallen off another car, rain water, coolant, oil, or any number of things that are not normally on the track. This flag will be displayed for one or two laps and then be withdrawn so it can be reused if a new condition develops.