Blood type refers to the classification of blood based on the presence or absence of specific antigens on the surface of red blood cells. The main blood type systems are the ABO system and the Rh factor. The ABO system categorizes blood into four types: A, B, AB, and O, depending on the antigens present. The Rh factor indicates whether blood is positive (+) or negative (-) based on the presence of the Rh antigen. Knowing your blood type is important for medical reasons, especially during blood transfusions or organ transplants. Mismatched blood types can lead to serious complications. Additionally, blood type may influence certain health conditions and dietary needs, making it a topic of interest in both medicine and nutrition.