From a Subscriber:
*warning* I have been drinking so please excuse my spelling, grammar, and other errors I make in typing this.
The idle adjustment knob on your motorcycle does the exact same thing it does on a carb'd bike. It adjusts the butterfly valves on the throttle bottles! These guys control the amount of air flowing into your engine and are directly connected to your throttle! (and can also control the amount of fuel coming in as well if you have vacuum operated carbs but that is another story). The knob is connected to a screw so righty tighty and lefty loosey, y'know the drill.
Anywho, the valves are nearly at the closed position and the the idle screw turns in to let in slightly more air raising the idle just as you would twist on the throttle to raise the rpms and you can screw it out which moves the valves closer to FULLY closed position letting less air through same as letting off the throttle.
Now there may or may not be some sort of automatic choke that goes beyond the set warm idle screw and that would obviously be controlled by a small motor and your bike's brain. On my '06 Triumph D675 ALL OF IT IS CONTROLLED BY THE BRIT BRAIN. You have to go into the ECU to set a new idle... but I can pick individual idle settings for different Engine temperatures which is kinda neat.