Humans must get Vitamin C through their diet, because they cannot actually synthesize it, unlike most mammals.
One of the most important functions of Vitamin C is its antioxidant capabilities. Vit C helps the immune system improve its function. Vitamin C is essential to the production of collagen in the body. Collagen literally holds the body together, and is most concentrated in the skin, tendons and blood vessel walls. It is thus important for the growth and repair of tissues in all parts of your body. It is needed for healing wounds and for repairing and maintaining bones, teeth and musculoskeletal tissues.