Coolant is a fluid used in engines and machinery to regulate temperature and prevent overheating. It absorbs heat generated during operation and circulates through the system, transferring heat away from critical components. Common types of coolant include water, antifreeze, and specialized chemical mixtures. In vehicles, coolant is essential for maintaining optimal engine performance and longevity. It flows through the radiator and engine block, ensuring that the engine operates within a safe temperature range. Proper coolant levels and maintenance are crucial to avoid engine damage and ensure efficient operation.