An air cooler is a device that cools the air in a room or space. It is also known by other names like evaporative cooler, swamp cooler, and desert cooler. The evaporative cooler uses the principle of evaporation to cool the air. The air is passed through a wet cooling pad or media, and as the water in the pad evaporates, it cools the air passing through it. The swamp cooler is a term used mainly in the southwestern US, where it is popular in hot, dry climates. The desert cooler is another term used in India and other parts of the world where it is used to cool homes and buildings. All these terms refer to the same type of cooling device that provides relief during the hot summer months.