A nutrient is a substance that provides nourishment essential for growth, maintenance and repair of living organisms. These substances are obtained from food or through supplements and help in various bodily functions such as metabolism, digestion, immune response, cell formation, and tissue repair. Nutrients include macronutrients like carbohydrates, proteins, fats, vitamins, minerals, and water. They are essential for the proper functioning of our body and play a crucial role in maintaining good health.