Nutrition is important for the normal function of the body, and various foods contain different nutrients. The major nutrients that are present in different foods are energy, protein, carbohydrates, fat, vitamins, and minerals. Along with these, some bioactive compounds that are present in foods are known as “phytonutrients”, which play a very important role for the health of humans. Phytonutrients have a tremendous positive effect on the human healthcare system, and they have medicinal properties, so they provide health benefits in the prevention and treatment of various diseases. Phytonutrients also play a crucial role in modulating the immune function from the prevention of specific diseases. As it is a natural product, it has no side effects that are usually present in drugs, chemotherapy, or radiotherapy. As well as they are quite cheap, so they significantly decrease the health care cost. It is basically a plant nutrient that has specific biological activity, which is helpful for human health. Some important phytonutrients are polyphenols, flavonoids, terpenoids, resveratrol, carotenoids, anthocyanins, limonoids, glucosinolates, phytosterols, phytoestrogens, omega-3 fatty acids, and probiotics, etc. They have specific medicinal properties, including antioxidants, antimicrobials, anticancer agents, anti-inflammatories, anti-allergics, antispasmodics, anti-aging agents, neuroprotectives, antidiabetics, etc.