What is the function... Vaccum "motors" or Solenoids (Solenoid is the better name I think) Operate "Gates" or Doors in the air flow (Panels that direct the air flow)
One door bypasses the heater core so you get COLD air (Unless they control it with a water valve) More doors either allow fresh air in or recirculate internal air... and direct it to the floor. dash or windshield.. (Windshield is the "all off" or default setting.. Apply vacuum to one of the devices it pulls a lever and changes the air flow for your comfort.