Spice rub is any mixture of ground spices that is made for the purpose of being rubbed on raw food before the food is cooked. The spice rub forms a coat on the food. The food can be marinated in the spice rub for some time for the flavors to incorporate into the food or it can be cooked immediately after it is coated in the rub. The spice rub can be left on or partially removed before cooking.
Seasoning is the process of adding salt, herbs, or spices to food to enhance the flavor.