When cooling, the evaporator in the indoor unit is called the evaporator, absorbs heat and evaporates, releases the cold, and the condenser in the outdoor unit condenses and releases heat. When heating, the condenser in the indoor unit is condensed and released. Heat, called the evaporator in the outdoor unit, absorbs heat and evaporates, and releases cold. Things are still two things, only one set, just because the work is different, the functions are converted to each other. Switched by a reversing valve.