1993 Jeep Cherokee Identifying Part

Heater problem
1993 Jeep Cherokee 6 cyl Four Wheel Drive Automatic 145K miles

Please help me identify this part (I'm a beginner.) It has heating hoses connecting to it, and the top black plastic "cap" is cracked in half (center of picture attached.) What is this part called? It's located in the back left of the engine, with some of the hoses going into the wall in front of the passenger seat. Thank you so much.