RE: How Many Channels?
A governor basically regulates and keep the head speed constant no matter how muchy throttle/pitch you apply. Without one you need to take particular care to set up a proper throttle curve, specially in IDLE UP mode.
Without a governor you might find when you do some hard 3D manuevres that the head suddenly speeds up after you have applied full throttle/pitch and go back to zero pitch such as a fairly violent stall turn or doing tick-tocks.
It basically has 2 magnets on the engine fan and a sensor, and then you set the head speed that you want on the governor and it will keep it there no matter how you fly.