Air Conditioning (split system)
An air conditioner works with one outdoor unit that compresses and delivers refrigerant to the inside coil, via copper lines. The air handler blows air passed the cold coil which removes the heat from the air which is delivered to the rooms via forced air ducts.
Evaporative Cooler (swamp cooler)
An evaporative cooler is a device that cools air through the evaporation of water. Water is pumped from a reservoir on the bottom of the unit over the top and onto the side of the unit. It is there that the water soaks pads which the fan blows air through the water and into the house.
The warm air that is drawn through the water causes the water in the pads to evaporate. The evaporation is caused by a transfer of heat from the air to the water. So the air going into the home has heat removed from it so it is now cooler and this cooler air is blown into the home. Since the air is coming into the home from outside, a window or door should be open on the opposite side of the house.
Evaporative cooling is an efficient way to cool a house.
Whole House Fan
A whole house fan is a fan that is normally placed in the ceiling of a home and vented to the attic. It works in conjunction with open windows or doors on the low level of the home, normally in the evening when the air is cooler outside than inside. The fan is turned on drawing air from the open windows through the house and out into the attic. The cooler air drawn through the house cooling the inside air, walls furniture and other thermal mass while evacuating the warmer air.
Evaporative coolers are inexpensive to buy and install and are inexpensive to run. The drawbacks are that the air must be cooler outside than inside so when you get home from work the house cannot be cooled until the air outside is cool. Another drawback is that they pull in outside air along with its pollutants such as dust, pollen, pollutions, etc. They are known to create a lot of dust and poor indoor air quality.