There are four types of air conditioner systems available.

Central air conditioning units live entirely outside the building, separate from the area to be cooled. Hot air is pumped out of the house while cool air is distributed throughout the building by way of ducts.
Split-systems, have 2 separate components; the motor of the air conditioning unit lives outside the building whilst the air outlet of the system remains inside.
A Stand Alone/Portabletype of air conditioner is a single movable unit can be easily moved to whatever room needs to be cooled.
A Thru-Wall/Window air conditioner is a single unit mounted through a wall or window. Part of it is inside the building and part sticks through to the outside.