MAV_TYPE in Airframe Config File


I’m trying to understand what “MAV_TYPE” in airframe config file is.
(airframe config file: PX4-Autopilot/ROMFS/px4fmu_common/init.d/airframes at master · PX4/PX4-Autopilot · GitHub)

I looked at the parameter list below for MAV_TYPE. But, still I cannot find the clear definition.

So, what is the MAVLink airframe type?

Also, for VTOL, I see several types as follows.
MAV_TYPE 22: VTOL reserved 2
MAV_TYPE 23: VTOL reserved 3
MAV_TYPE 24: VTOL reserved 4
MAV_TYPE 25: VTOL reserved 5

What is the difference in these types?

I am also wondering about the answer to this question.
I see this in the source:
“The type of the MAV and Autopilot hardware allow the receiving system to treat further messages from this system appropriate (e.g. by laying out the user interface based on the autopilot).”

Anyone can answer to the above question? Thank you very much for your help in advance.

Is there any idea about this topic?