Thank you, it was transmission oil.The one that goes to your radiator is called coolant or antifreeze. It may be greenish in color depending on type. If you touch it, it feels like water.
Another fluid is called transmission oil. I'm not sure if this is true for all cars but on our old car, there is a hose connection to the radiator that leads to the transmission.
It doesn't matter if it is oil or water, it should be checked and rectified as soon as possible. You don't want to run the car with such leak.