There are four major blood groups determined by the presence or absence of two antigens -A and B - on the surface of red blood cells. In addition to the A and B antigens, there is a protein called  the Rh factor, which can be either present (+)  or (-), creating the 8 common blood types. They are, A+, A-, B+, B-, O+,O- and AB+,AB- .

Group A has A antigen on the red cells but B antibody in the plasma.

Group B has B antigen on the red cells but A antibody in the plasma.

Group AB has A and B antigen on the red cells but neither A  nor B antibody in the plasma.

Group O has neither A  nor B antigen on the red cells but both A and  B antibody in the plasma.