When an air conditioner is set to the "fan" mode, it circulates the air from inside your home without actively cooling it. In this mode, the air conditioning system's compressor is not running, which means it does not cool or dehumidify the air. Instead, the indoor air is drawn through the air handler or the indoor unit, and then the fan blows this air back into the living space.
The primary purpose of the "fan" mode is to improve air circulation and distribute the existing air throughout your home. This can help create a more even temperature throughout different rooms and can also aid in maintaining indoor air quality by filtering and removing particles from the air.
If you want to cool your home, you should set the air conditioner to the "cool" mode, which activates the compressor and allows the system to draw in outdoor air, cool it, and then circulate the cooled air indoors.