Vitamins are substances that the body needs and utilizes to function properly. They are organic chemicals that our body cannot produce on its own and so they must be ingested or absorbed. Vitamins help the body in countless beneficial ways, and life would not be possible without the presence of ALL of them. Because of this, it is important that they be obtained as recommended.
Supplemental forms of vitamins are acceptable substitutes. Supplemental vitamins are still organic, they are just compressed. They are still obtained from animals and plants (unless it is a completely synthetic material to begin with).
Supplements can replace the vitamins obtained from food, but nothing else. They certainly can not replace food itself. Vitamins do not give the body energy, calories, carbohydrates, or protein (which are all necessary nutrients that must be obtained from food).
Vitamins work with the body's enzyme system, a system of chemical reactions, product breakdown, and organ function. Through this system, vitamins supply power to our bodies like electricity to a television. Even though we only intake vitmains at a fraction of the amount in which we intake proteins, fats and carbohydrates, we need them just as much. Although they only make up a microscopic portion of our diet, they are probably the biggest factor in judging how healthy we are.
Basically, Vitamins are digestet. Like food (or aything entering the stomach), Vitmains are broken down by specific enzymes into more simple components and then absorbed through the intestines into the bloodstream. From there they are delivered to all the cells of the body where they carry out their function.