Milk is processed on the basis of the maximum content of fat and solid not fat (SNF) it would ultimately possess.

Standardized milk
Whole milk
Reduced-fat milk (2%)
Low-fat milk (1%)
Skimmed milk/non-fat milk

Reduced-fat milk (2%): This milk contains 2% milk fat. The percentage of milk fat refers to the percentage of fat by weight, and much of milk's weight is water. Once you subtract the water from 2% milk, for example, you're left with a product that contains 20% fat by weight; such milk actually derives 35% of its calories from fat. Drinking 2% milk is a good way to wean oneself from whole milk at first, but is too high in fat as a permanent choice, unless your diet is otherwise very low in fat.

Low-fat milk (1%): One-percent milk gets 23% of its calories from fat. Many people find low-fat milk more appealing and a good compromise.

Skimmed milk/non-fat milk: This type of milk has as much fat removed as possible. It may not contain more than 0.5% milk fat by weight, and usually contains less than 0.5 gm of fat per cup, deriving just 5% of its calories from fat. Skimmed milk has about half the calories of whole milk. It is the best choice for adults, and is the only type of milk that should be consumed by people on strict low-fat diets. Unfortunately, skim milk has a very "thin" flavor and an unappealing bluish cast.