How do blood types differ from one another in the abo blood classification?

Blood types in the ABO classification differ based on the presence or absence of specific antigens on the surface of red blood cells. There are four main blood types: A, B, AB, and O. Type A has A antigens, type B has B antigens, type AB has both A and B antigens, and type O has neither. Additionally, the presence of antibodies against the missing antigens in each type determines compatibility for blood transfusions.