Of the heating and cooling load, it is due to latent heat. In the case of cooling, it is a load that tries to increase the humidity in the room by means of heat generation of the human body, respiration moisture, water vapor, and moisture brought in by the outside air, etc.
Or, in the case of heating, it is a load that tries to reduce the humidity in the room by means of drafts and outdoor air loads, since the outside air is absolutely low in humidity.