What does the two-way fresh air of Haier air conditioning mean?

This is Haier's patent, which means that the dual fresh air device has two fans. One fan sends outdoor fresh air indoors, and the other fan discharges indoor dirty air outdoors. In the process of conveying fresh air and exhausting dirty air, the two kinds of air completely exchange heat and humidity through the total heat exchanger, so as to recover heat energy and humidity, get fresh air and exhaust dirty air. During the whole exchange process, the two gases will not mix.