Hemoglobin is a vital protein found in red blood cells that plays a crucial role in transporting oxygen from the lungs to the rest of the body. It consists of four subunits, each containing an iron atom that binds to oxygen, allowing for efficient oxygen delivery to tissues and organs. In addition to oxygen transport, hemoglobin also helps in carrying carbon dioxide back to the lungs for exhalation. Abnormalities in hemoglobin can lead to various health issues, such as sickle cell disease and thalassemia, highlighting its importance in maintaining overall health.