Blood groups are classifications of blood based on the presence or absence of specific antigens on the surface of red blood cells. The most well-known blood group systems are the ABO system and the Rh factor. In the ABO system, blood is categorized into four main types: A, B, AB, and O. Each type can be either positive or negative, depending on the Rh factor, which is another antigen. Understanding blood groups is crucial for safe blood transfusions and organ transplants. If a person receives blood from an incompatible group, it can lead to serious health complications. Therefore, knowing your blood type can be lifesaving in emergencies and is essential for medical procedures.