It's steam from boiling coolant (or water) coming out of the overflow hose connected to the top of the radiator just below the level of the cap.
Signs of your battery exploding can be swelling overheating and a hissing noise
my car isn't steaming only in drive but not overheating.
If it it shutting off because of the hissing, it is likely moisture getting at electronic parts and shorting them. The hissing would be caused by cold water contacting hot engine parts. If the hissing is only heard after YOU shut off the car, it is likely a small leak in a vacuum hose. These are usually easily fixed.
It is overheating. Possible causes are thermostat stuck closed, defective water pump, cooling fan not working, clogged radiator, and more. STOP drivng this car until you get this fixed. You are going to ruin this engine if you have not already done so.
Your car is overheating when idle because there may be a lack of oil or water in the engine. It can also be a problem with the engine itself. If your car is overheating, simply contact a wrecker or a road assistance company. The police are also available to assist you.
You should not buy a car with overheating problems. This means that it will not serve the purpose and will develop other mechanical problems.
your car is broken
It means the car is overheating.
There are several reasons why your car may be overheating. Check the thermostat to be sure it isn't stuck. If the car revs up and down, the timing may need to be adjusted.
Faulty Vacuum Brake Booster.
Exhaust leak? Vacuum leak?
Either the water pump impeller is loose on it's shaft, or you have a leaking head gasket.