Meaning of flags in go-karting
While karting, you will encounter different flags (both physical and digital). Below I try to explain it for you so you know what to do when you encounter a flag.
Before karting, always check the regulations of the karting track so you can be sure what the rules are, as they can vary from one karting track to another.

Green flag
Track clear. You may resume racing at full speed.
Green flag can also be waved at the beginning of the race or heat. This means that the race or heat has started.

Yellow flag
When the yellow flag is waved, the marshal gives a warning. This may happen if there has been an accident or if a kart has collided with the guardrail and is blocking the road. This also means no overtaking and driving slowly during the yellow flag.
Double yellow flags normally mean that there is danger on the track. However, they are more serious than single yellow flags. Instead of one part of the track being yellow-flagged, a double yellow flag means the entire track is yellow-flagged.
This means you must slow down your kart and not overtake anywhere on the track until the green flag is shown. Full course yellows are normally shown when debris or a stricken kart needs to be removed from the track. Slowing down the karts throughout the lap gives the marshals more time to remove the obstacle from the track.

Red flag
When you see a red flag, you must immediately and in a controlled manner stop your kart. No kart may continue driving if the race is stopped. Do not get out of your kart unless you are instructed that the race is permanently stopped. If the red flag indicates a temporary stop, the marshal will signal you to proceed as soon as the danger has passed.

Blue flag
If you see this flag, it means that you are being overtaken by a faster driver and you have to give way. The best thing to do in this scenario is to move out of the racing line so that the kart behind you can overtake safely and no accidents happen. There is nothing wrong with being overtaken, but we must give priority to more professional drivers, especially on a crowded kart track.

Red and yellow striped flag
This is one of the flags that is not often used in go-karting. In fact, it is not often seen in any other motor sport either. Still, there may be circumstances in which you see it, and you should know what it means.
This flag indicates to drivers that the track in front of them is slippery. This may be due to oil on the track or some other slippery substance. The flag can also be used to indicate that there may be an animal, debris or obstacle on the track. In many cases, the yellow flag is then used.

Black flag with orange circle
This flag is displayed with a go-kart number. It indicates that a go-kart is being summoned to the pits due to serious mechanical problems or loose bodywork that presents a risk to other competitors. Also known as the 'Meatball' flag.

Per-bend black/white flag
This is the warning flag. If you see this flag, it means you have violated the rules in some way. This could be anything from exceeding course limits to unsportsmanlike conduct.
In most cases, you get to see this flag three times before you are penalized or disqualified, depending on the severity of your actions. In some cases, you will be shown this flag with your start number if you do not acknowledge having seen it.

Black flag
When you see the marshal waving a black flag at you, you must immediately stop driving recklessly and unsafely. This can happen to you if you have collided with objects on the track or other karts during the race. If you see this flag, get to the pit-lane as quickly as possible (but also as safely as possible!). The marshalls there will then tell you why you got the black flag. It does not have to be that you are driving recklessly, it can also be a safety issue like your seat belt is loose, or your helmet is not properly fastened. In most cases, you are then allowed back on the track to continue racing.
In the worst case scenario, the black flag means that you are disqualified in the heat or race and may not continue driving!

White flag
The white flag is used to show drivers that they are starting the last lap of the race. The white flag is not used at all karting tracks, but when you see it, it simply means the race is almost over.

Checkered flag
The checkered flag is used to indicate the end of a session. The flag can be used at the end of practices, heats, qualifications or races.