When most people thing of air conditioners, and image is formed in their mind of a machine that magically blow cold air into their home.  It doesn’t matter whether it is a portable air conditioner, or a window air conditioner, or even a central air conditioner.  The end result is the same, cold air.  However what is actually happening is not so much that cold air is being created but that heat is being removed from the air that is already in your home and recirculated.  The best way to visualize this is my noting where the air filter is located on your air conditioning system and where exhaust or heat is being expelled from the system.

If you are talking about a portable air conditioner then of course the air is coming from within the living space that you are cooling, but you should also have an exhaust duct connected to the rear that sends hot air outside.  In the case of a window unit, air is not being blown in from the outside.  It is sent through the filter which is located inside of the window, then the heat is removed and expelled through the rear along with any condensation and the th same air is blown back into the room.  With a central air conditioning system, the compressor on the outside of your home is also the means of expelling the heat removed from the home.  If your air conditioner is working properly then hold your hand above the compressor while it is running and you will be able to feel the heat being removed from your home.

All of this magic occurs as a result of the compression and expansion of the refrigerant chemicals inside of your air conditioning system.  Have you ever used a can of compressed air to clean out your keyboard?  Do you remember how cold the can became as you continued to spray air out of the can?  This is a very simplistic form of the same process that is happening within your air conditioner.  Instead of the air (or coolant) leaving the can, it is moved from high pressure to low pressure then compressed back to high pressure to start the process over again.