Condenser
(Single stage)
A condenser unit is used to cool down and condense incoming refrigerant vapor into liquid, a compressor to raise the pressure of the refrigerant and move it along, and a fan for blowing outside air through the heat exchanger section to cool the refrigerant inside
Condenser
(two stage or variable speed)
Two-stage cooling refers to the type of compressor that's in the outside condensing unit. This feature allows for two levels of operation depending on your cooling needs — full capacity on hot summer days or part capacity for milder days.
While these units are more expensive in comparison to their single stage counterpart, having a 2 stage set up can ultimately save you more money on your electric bill.
Air Handler (coil)
An air handler is a device used to regulate and circulate air as part of a heating, ventilating, and air-conditioning (HVAC) system