Bagpipes all work basically the same way - there's a bag to hold air and one or more pipes coming off it to produce sound. For many types of pipe, the sound-producing pipes consist of a chanter, which has holes that may be opend and closed to produce a melody, and one or more drone pipes, which play a constant note to provide background. The Great Highland Bagpipe, for example, has a chanter and three drones, a bass and two tenors. The chanter is capable of nine notes from G to the A above the octave G. The drones play an A to provide background. (This is all somewhat simplified.)

One of the main divisions of pipes is the way in which air gets into the bag, whether mouth-blown or bellows-blown. The GHB are mouth-blown pipes; there's a tube into which the player blows to fill the bag and to keep it full as he plays. The uillean pipes are bellows-blown - the player wears a bellows attached to a belt and to his arm, so that by moving his arm he can pump air into the bag. This also allows uillean players to sing along while they play, which may or may not be a good thing. Going from one type to the other therefore requires some adjustment of playing style. In the GHB, I blow the bag up until just before the drones start to sound, strike in (strike the bag with my right hand so that all the drones start at once at the correct pressure) and then bring in the chanter. As I play, I adjust the pressure of my arm on the bag, lessening the pressure when I'm blowing into the bag and decreasing it when I'm inhaling. The uillean pipes require the same sort of thing, but the increse and decrease in pressure from your arm is directed by the action of your bellows arm. (That part is more theoretical to me; I've never played a bellows-blown set of pipes.)