You should choose the HEATING mode when you want your Air Conditioner to control the temperature of your room using only heating.
For example: If you chose 25 ° C and your environment is colder than 25 ° C, the Air Conditioner will run in Heating to maintain the ambient temperature at 25 ° C and whenever the temperature drops, the unit will again operate to raise the temperature of your room to 25 ° C. But if your environment is hotter than 25 ° C, the unit will not trigger the Cooling cycle, keeping only the fans on.
Whenever the temperature of your environment is above or around the chosen temperature, only the fan remains operating.
Sometimes while it is running, the air conditioner will perform the defrost operation of the condenser. During this operation the fan of the indoor unit will be turned off.