Hi Cands,
If you have 2 thermostats, you probably have two air conditioners. One thermostat controls both the furnace and one of the air conditioners. Usually that would be the air conditioner for the living room. The other thermostat controls just the 2nd air conditioner, usually the bedroom. If both units are ducted together, the only clue to how the air conditioners are running might be the noise made by fans and compressors.
I've heard of a few model/floor plans where the thermostat that controls the furnace is located in the bedroom.
Most air conditioners are just air conditioners. Others are heat pumps which can either heat or cool, and others may come with heat strips. So it's possible your 2nd thermostat may do more than just cool, depending on how the rig was ordered. But again, most are just air conditioners.