The coolant runs in a tireless cycle, as it removes heat from your engine during operation. It goes through the compartments around your pistons and cylinder heads. It repeats its journey until it gets hot enough, and then it hits your radiator.
Car radiators are designed to distribute excess heat carrier fluid into the atmosphere. They are made of conductive metals for fast heat transfer. They are also designed to balance the increased surface area with the lowest possible pump pressure requirements. This is important because the process gets rid of heat that would otherwise melt your engine to an unrecognizable piece of metal. In short, your radiator allows your engine to perform its basic functions for extended periods of time without damage.