Fat-free milk is essentially the same thing as Skim milk (also called non-fat milk). Fat free milk is just the new term for marketing Skim milk which has 0.5% or less fat.
United States Department of Agriculture (U.S.D.A.) recently changed the laws for labeling milk. Four types of milk are now recognized by the USDA. These different types of milks are differentiated on the basis of the amount of fat (cream or butterfat) present in each of them. Following are the types of recognized milk:
1) Whole milk - Minimum fat - 3.25%
2) 2% Milk - Reduced fat - 2.0 to 2.5%
3) 1% Milk - Reduced fat - 1 to 1.5%
4) Fat Free Milk - 0 to 0.5% Fat