Blood groups and types are categorized based on the presence of antigens and antibodies in the blood. The four main blood groups—A, B, AB, and O—are determined by the ABO system, while the Rh factor adds another classification as positive (+) or negative (-). Knowing your blood type is essential for safe blood transfusions, medical emergencies, and pregnancy care. Each type has unique compatibility, influencing who can donate or receive blood. Understanding these distinctions promotes better healthcare and lifesaving practices.