A heater core is a small radiator-like device found in vehicles, responsible for providing heat to the cabin. It works by circulating hot coolant from the engine through its core, allowing warm air to flow into the interior when the heater is turned on. Typically located behind the dashboard, the heater core is connected to the vehicle's cooling system and HVAC (heating, ventilation, and air conditioning) system. If the heater core leaks or becomes clogged, it can lead to reduced heating efficiency or even coolant loss, which may affect the overall performance of the engine.