Rubs come in two forms, wet and dry. The dry rub is comprised of sugars, salt, spices and herbs and is sprinkled or rubbed into the meat. The wet rub usually contains an oil and is rubbed into the meat. The rub is supposed to enhance the flavor of the meat. You want to put it to the meat, not the fat or skin of the animal so as to flavor the meat. With pork, it is best to score the fat down to the meat muscle so as to make it possible for the flavors to get to the meat instead of running off with the fat. With chicken, apply it under the skin instead of on top of the skin. The variety of spices is endless as they can vary to ones tastes.