Vitamin C or L-ascorbic acid, or simply ascorbate (the anion of ascorbic acid), is an essential nutrient for humans and certain other animal species. Vitamin C describes several vitamers that have vitamin C activity in animals, including ascorbic acid and its salts, and some oxidized forms of the molecule like dehydroascorbic acid. Ascorbate and ascorbic acid are both naturally present in the body when either of these is introduced into cells, since the forms interconvert according to pH.
Vitamin C is a water-soluble vitamin, meaning that your body doesn't store it. You have to get what you need from food, including citrus fruits, broccoli, and tomatoes. You need vitamin C for the growth and repair of tissues in all parts of your body.
Ascorbic acid is also widely used as a food additive, to prevent oxidation.