Image above shows how the Cooling System works with the engine to keep the engine cool. If the Cooling System Leaks then Antifreeze Coolant will come out of one of the locations in the picture.
Most cars use a pressurized antifreeze coolant liquid cooling system to keep the engine at the best operating temperature. This antifreeze coolant is usually a florescent green or orange in color and freezes at lower temperature than just plain water. The antifreeze coolant liquid also contains chemicals that prevent damage through corrosion to the parts of the engine and cooling system the liquid flows through.
A Cooling Fan located beside the radiator helps to cool the antifreeze coolant in the radiator. Cooling fan or fans suck or blow air across the radiator. Since the air is cooler than the antifreeze coolant liquid in the radiator, the heat from the liquid will transfer to the air. This reduces the temperature of the antifreeze coolant.
Water pump, pumps the cooler antifreeze coolant back into the engine which cools the engine down.
A Thermostat makes sure that not too much cooled antifreeze coolant is pumped back into the engine. If too much cooled antifreeze coolant was pumped back into the engine, then the engine would get too cool. A cool engine does not run efficiently as an engine at the right temperature.