There are many brands and configurations of air conditioners.
There are some air conditioners called “packaged systems” that only have ductwork entering the home. “Mini-splits” are another common type. These are a mix between a traditional split system and a packaged system. All of the AC unit equipment is housed outside the structure but has a wall-mounted air handler inside. These are common in mobile homes, additions and external structures like detached garages or outbuildings.
Most homes have a more typical “split system” The typical air conditioning system has an “Indoor Unit” consisting of an evaporator coil and a blower, and an “Outdoor Unit” that contains the compressor(s), an outdoor coil and a fan which is collectively called a Condensing Unit.
The outdoor unit compressor pumps the refrigerant through the system to gather heat from inside the home and remove it from the outside. In the process, heat and moisture are removed from the indoor air of the home by blowing warm, moisture-laden air over the cooled indoor evaporator coil. The moisture from the humid air condenses on the evaporator coil and drips down into the drain pan where the water collects and is piped to the condensate drain.
The heat that gets transferred to the evaporator coil transfers to the refrigerant and is carried to the condensing unit outside where the refrigerant gives up its heat to the outside air by way of the outside coil and fan. The cooled refrigerant then goes back into the home to remove more heat and humidity.
AC Units must be properly sized to the airflow and cooling needs of the home. The exact same sized home can have different cooling needs based on its exposure, tree cover of the lot and its proximity to water.