Do you need antifreeze to drive your car?

No, but antifreeze has corrosion inhibitors in it's formula. These help to stop corrosion forming internally, and will also protect the head gasket from corroding.

Antifreeze added to the water in your cooling system lowers the freezing point of the coolant, preventing the liquid from freezing in the cold winter. It also raises the boiling point of the coolant. If you drive your car with water and no antifreeze, your car will heat up and the water will get hot enough to boil over. With antifreeze, the coolant will continue to do its job of keeping the engine from overheating which can result in damage to the engine.