Proteins are essential macromolecules composed of amino acids, which play a critical role in building and repairing tissues, producing enzymes and hormones, and supporting overall bodily functions. Found in a wide range of foods, proteins can be classified into two main categories: animal-based sources, such as meat, fish, eggs, and dairy, which contain complete proteins with all essential amino acids, and plant-based sources, like legumes, nuts, seeds, and whole grains, which may offer incomplete proteins but can be combined to provide all necessary amino acids. Adequate protein intake is vital for muscle growth, immune function, and maintaining a healthy metabolism, making it an important component of a balanced diet.