Heat pump, or straight cool.

A straight cool system only moves heat one direction: out of the house. Heating, if the house has any, comes from something else entirely, usually a gas furnace sharing the same ducts.

A heat pump is the same machine with a valve that lets it run backwards. In summer it pulls heat out of the house. In winter it pulls heat out of the outdoor air and puts it inside. The extra component is a reversing valve.

Both are extremely common in the Valley, which is why it is worth knowing which one is bolted to your house.

Telling them apart

The model number on the outdoor unit data plate is the reliable answer, and anybody working on it will read it.

Rougher tells: if your thermostat has an emergency heat or aux heat setting, you almost certainly have a heat pump. If you have a gas furnace in the garage or a closet and the outdoor unit only runs in summer, it is straight cool. A heat pump outdoor unit runs in winter too, and will occasionally steam while it defrosts.

Why it matters when something breaks

Most of what fails is identical: capacitor, contactor, fan motor, coil, drain. Those repairs do not change.

What changes is the extra ground a heat pump gives you to lose. A stuck reversing valve can leave a heat pump cooling when it should heat, or heating when it should cool, which reads to a homeowner as a completely broken system when the compressor is fine.

A system blowing warm air in July is worth checking for a mis-set thermostat or a reversing valve problem before anybody starts talking about refrigerant.