brining is, you are basically soaking them for a few hours in liquid of some sort. with spices added. you can use tender quick cure, salad dressing, buttermilk, the choices are about endless. mix up your favorite concoction and give it a try. what you are doing is imparting another flavor and moisture into the chicken.
you can also spritz or mop while you are smoking to add flavor and moisture.
you also use brining or curing when you are making things like belly bacon, canadian bacon , ham , pastrami, corn beef and the like.
get yourself the bible of sausage making and cureing meat, by Rytek Kutas. it will help you become an expert at it all.