Helper bags only go on the rear between the frame and the axle and only help hold the rear up for heavy loads. So daily driving you will have almost no air pressure and it will ride like normal, but when you put a trailer or a bed full of stone or something you put more air into the helper bad to keep the back of the truck from sagging and bottoming out.
regular air ride bags are made to handle the whole load of the truck. and they are what holds the truck up instead of coils/torsion bars/ leaf springs
If your talking about just the difference between the bags themselves, a helper bag doesnt have the range of height that a air ride bag does, and isnt as tough as a air ride bag.