The condenser and compressor are located outside of the house, while the evaporator is located inside the air distribution system. The quantity of heat that needs to be removed to maintain indoor comfort, on a specific warm day for your region, is known as the heat gain for your structure*. A building gains heat from the actual outdoor temperature and humidity levels. It gains heat from the people inside of it, from the lights, computers, copiers, dishwashers and ovens. But mostly it gains heat from its exposure to sunlight, from solar radiation. The hot sun beating down on the walls and the roof, the sunlight pouring through the windows and warming the floors it lands on.
The sum of all of this heat accumulation is known as the heat gain of the building.