Packaged Terminal Air Conditioners are typically seen in hotel rooms but as they develop and become quieter, they are finding their way into more and more residential applications.
At the heart, Packaged Terminal Air Conditioners are another type of thru-the-wall air conditioner but they come in a very different form factor. Beware, some manufacturers call their products "DIY" but you can void the warranty if you do not have it installed by a licenced HVAC technician or electrician.