Vitamins are micronutrients that are essential for proper body function. They are required in small amounts but play crucial roles in various metabolic processes such as metabolism, immune system function, and cell growth and division. There are 13 vitamins, classified as either fat-soluble (A, D, E, and K) or water-soluble (B-complex vitamins and vitamin C). Some common sources of vitamins include fruits, vegetables, dairy, meat, and fortified foods.