See here for a full comparison of the different types of A/C you can buy.Window Air Conditioner:This is a small unit that contains all of the main components that fit into a little box that is put into your window. Generally used to cool small spaces or individual rooms in the home .Split air conditioner or mini-split:Comprises of two parts;  an indoor and outdoor component. A split air conditioner is slightly smaller and more aesthetically pleasing than a window air conditioner and can cool one or two rooms in the housePackaged Air Conditioner:This is the large HVAC unit that is outside of the home. It hooks up to your homes furnace and circulates the cool air through all of the duct work.  It is the most expensive of the three options however it also cools the entire house instead of one or two rooms.