In school I've always been taught that they are two important and different US policies, but to me they seem like different ways of stating the same thing, i.e. "Communism exists, try to contain it by not letting other states become communist." Was there any functional difference between the thinking behind both theories? Did US policy reflect any difference from one to the other?
The Domino theory was the idea that once one state went communist, other states in the region would follow. Containment was the strategy to combat the domino theory.