Basically, if you look at it, a window air conditioner is a less efficient and compact split air conditioner. Split air conditioners are made up of two components, the indoor air handler unit and outdoor condenser unit. A window air conditioner is one sall compact machine that cools/heat your room. Window ac are cheaper to install as well. But split air conditioners are usually more powerful then window ac and provide better energy efficiency. On top of that, split air conditioners do not need an exterior wall to install and they can be used to provide cooling and heating solution for more then one room.