Vitamins are organic molecules that are essential micronutrients obtained through diet. They function as cofactors in enzymatic reactions and have various roles including vision, bone formation, antioxidation, and blood clotting. There are two types of vitamins - fat soluble vitamins A, D, E, and K which are stored in the body, and water soluble B complex and C vitamins which are not stored. Vitamins play important roles as cofactors in many enzymatic reactions and metabolic processes.