There are parts of a car that can freeze on an icy and cold day. You may try to start your car and the engine just turns over and over again. The liquids in the car may freeze. Therefore, you need some sort of coolant or antifreeze, but that depends on what you are trying to accomplish. There are differences between these two things including the use of them.
If you are wanting to push the heat away from the engine because your engine might overheat in trying to make the liquids not freeze, then you will use coolant. Antifreeze lowers the freezing point of the liquids in the cars. They are also made with different things. Antifreeze is made with ethylene glycol, and coolant is made with half of the antifreeze and the other half is water.