was recently made aware that people think air conditioning pumps in air from outside. Cars are a bit different because they have a closed cabin mode but air conditioners work by using a heat exchanger and fan to recirculate the air in a space over and over until it gets to the desired temp. if it pulled in outside air it would either struggle to keep the temp down or not work at all
the back of the unit releases heat into the outside air with a heat sink. its outside because its dumping the heat (not the air! just the heat) from your dwelling, plus they put the motor + compressor out there because its loud. helps reduce the noise. central air is basically the same but they use a long pipe to move the coolant around to the unit outside.
this is also why you cant just plug in a window conditioner inside without installing it and expect it to work. net zero cooling effect
There is an exception to this, and it's single-hose portable AC units (the kind that sits on the floor and has a hose going to a window panel). The hose isn't pumping outside air in; it's pumping inside air out (after using it to cool the compressor), but the net effect is the same. The air has to be replaced, so external air finds its way in through the gaps and cracks and window edges. This is why single-hose units are less energy efficient and less effective than dual-hose units. They can still cool a small space pretty well, so they're great for small apartments, but it costs more energy to do so. Dual-hose units are exactly as OP said; they pull in outside air, use it to cool the compressor (i.e. absorb the heat the compressor has pulled out of the inside air), and pump it back outside.
This does mean that if you're running a single-hose AC unit in a place that has a lot of smoke or air pollution outside, you both will need more air filtration and will wear out your filters faster, since the unit is drawing more outside air into your home.
