Without more information I can only speculate. The units labelled A/C are probably your outdoor units. Whether they are actual heat-pumps (reversible for A/C and heat) I don’t know.
With these types of systems there is usually an Air-Handler (AHU) that has the blower and evaporator (reversible to be a condenser if it’s a heat pump). That they are labelled “Furnace” is probably because they contain electric heating elements. This is common in a central heat-pump system.
Why you would have 3 air-handlers and two outdoor units remains a mystery as they are usually one-one, but It’s possible one doesn’t have A/C. You should be able to identify the three AHUs as they would need to be accessible to clean/change filters etc. Examine each one. The connection to the outdoor unit is usually pretty obvious as it requires two insulated pipes running to the outdoor unit, one quite a bit fatter than the other.
The model numbers on the outdoor units can be used to determine if they are bi-directional “heat-pump” or uni-directional (A/C only).