2002 Dodge Stratus coolant leaking and engine over-heating

Engine Cooling problem
2002 Dodge Stratus 6 cyl Front Wheel Drive Automatic

There is a piece mounted on top of the engine that has three hoses and two electrical connectors. One hose goes to the radiator, one to the resevor and one into the firewall. I need to know what this piece is and what it does exactly.