Blood typing is a laboratory test that determines an individual's blood group based on the presence or absence of specific antigens on the surface of red blood cells. The main blood groups are A, B, AB, and O, which are further classified by the Rh factor as either positive or negative. This classification is crucial for safe blood transfusions and organ transplants. The process of blood typing involves mixing a small sample of blood with antibodies that react with the antigens. If the blood clumps together, it indicates the presence of a specific antigen. Accurate blood typing helps prevent serious complications during medical procedures.