Zone refers to how many air-handlers the unit comes with out of box. Our Mini Splits come with either a single zone, dual zone, tri-zone or quad-zone setup. The listed condenser capacity will be divided between the zone outputs in multi-zone systems. For example, a 48000 BTU Dual zone Mini Split will have 2 - 24000 BTU zones. It is most ideal to get an air handler for each room, however, one air handler will be more than sufficient for multiple rooms as long as the total area you are trying to cool is within the limits of the unit's BTU capacity.