VRF stands for Variable Refrigerant Flow, and it is a type of HVAC system that uses refrigerant as the cooling and heating medium. It is a highly efficient system that can provide simultaneous cooling and heating, and it is capable of zoning different areas of a building to different temperatures. VRF systems are also known for their low noise levels and their ability to be easily integrated with other HVAC systems. They are often used in commercial buildings, but they are becoming increasingly popular in residential applications as well.