If we are to define air conditioning we will have to say that it is the mechanical way of regulating the temperature, humidity, cleanliness and air flow inside a room or a building. The job of an air conditioner would be to control the temperature-humidity ratio at such a level that that it is both comfortable for us and is also healthful. As most air conditioners come with a filter it also clean the circulating air of the various contaminants like dust, soot, pollen, etc. Although not to the levels of an air purifier, air conditioners do in fact clean air considerably.
What an air conditioner unit actually does is it draws in air from a room or a building and passes it across that side of the refrigeration apparatus which is much colder and absorbs the heat in the air. How cool the refrigeration apparatus is, is determined by how a thermostat is regulated. For water-cooling airconditioning units, the heat is drawn away by the water flow. So fundamentally the principle is simple.
However, there are a number of things that are associated with a modern airconditioner, which makes it more than just a cooling device. In fact if it remains just a cooling device, it would be actually wrong to call it an air conditioning unit. Ideally it should provide a comfortable temperature inside the room, no matter how hot or how cold is it outside. So many air conditioners come with a heat pump whose function is to just reverse the refrigeration cycle. So when it is chilling cold outside, you can still be warm and cozy inside.
Although the rudimentary ideas of the concept of air conditioning can be traced back to the early decades of the nineteenth century it was only in the first half of the previous century that air conditioner as we see it was introduced. Since then air conditioner had little stopping and it has become an integral part of our life.
Although we generally tend to associate air conditioning with the comforts of life, it is also crucial to carry out several processes. For example certain operations like an open heart surgery can be conducted only under a controlled environment, and without air conditioner that would not be possible. Many industries, including the chemical and pharmaceutical industries cannot do without air conditioning. In fact it is hard to conceptualize today's world without air conditioning.