Cold is another word for empty. It isn't really anything. It is, as a vacuum is, the lack of something. Cold is the lack of heat. The earth we live on is almost empty. We live on the edge of a delicate temperature balance only some 500° F above empty. The coldest it can ever get is about -460° F, but "hot-wise" temperatures can reach into the billions. We live at the bottom of a thermometer that stretches to the moon. Our planet is a cool puddle in a desert of heat, but water works only at these narrow temperature ranges, and life depends on this water.
Our planet must remain empty in order to support life. Refrigerants that leak into the atmosphere cause damage which allows extra heat to alter and fill our emptiness. Federal and international regulations have been devised and enacted to curb the release of certain refrigerants into the atmosphere to prevent our emptiness from being disrupted. A federal licence is required for handling these refrigerants. If your going to use refrigerants, use them conscientiously. Much depends on it.
It is the function of a cooling system to remove unwanted heat from a structure and relocate it to the out of doors. This heat exchange is accomplished by the use of the refrigeration cycle as performed by your air-conditioning sytem. The refrigeration cycle takes advantage of the relationships between pressure, temperature and volume; in such a way that heat is collected inside and released outside. It uses a condensor, a compressor, and an evaporator to accomplish this task.
The condensor 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.
* Many contractors distribute an extra 1500 btu of cooling to the kitchen to offset the heat given off by the appliances, and an extra 400 btu to various rooms for occupants.