The Daily Value are a set of suggested daily intakes of calories and selected nutrients, developed to use on food labels. The following chart lists them, for adults and children over 4 years old:

The Nutrition Facts panel on the back of a food label tells you what percent of the Daily Value is supplied by what the label says is a "serving" of the food. In a day, a reasonable goal is to consume 100% of the Daily Value for a nutrient. Take a look below at the vitamin C % Daily Value for a serving of the Odwalla product "Strawberry C Monster".

What that is saying is that a "serving" (the label says that a "serving" is 8 ounces, or half the bottle) has 1000% of the DV for vitamin C (10 times) what someone needs in a DAY. If someone drank the entire bottle (which is probably what most people would do), that would be 20 times. Since the DV for vitamin C is 60 mg, 20 times that much would be 1200 mg. One-half cup of a vitamin C-rich food like strawberries has about 40 mg of vitamin C. Upper Intake Levels (ULs) are U.S. standards that identify potentially hazardous levels of nutrient intake.