The most common HVAC system that can provide both heating and cooling is a split system. This system consists of two parts: an outdoor unit and an indoor unit. The outdoor unit contains a compressor, condenser, and expansion valve, while the indoor unit contains an evaporator coil and a fan. The outdoor unit is responsible for cooling the air, while the indoor unit is responsible for heating the air. The two units are connected by refrigerant lines, which allow the system to transfer heat from one unit to the other. This system is highly efficient and can provide both heating and cooling with minimal energy consumption.