Vitamins are organic compounds that are required in small amounts for normal growth, maintenance, and reproduction. They are classified as either fat-soluble or water-soluble. Deficiencies of specific vitamins can lead to diseases like scurvy, rickets, and beriberi. While vitamins are essential for health, excessive intake of certain vitamins can also be toxic. Maintaining a balanced diet is important to meet vitamin needs without risk of deficiency or toxicity.