The term 'blood group description' refers to the classification of blood types based on the presence or absence of certain antigens. The most common blood type system is the ABO system, which is based on the presence of A and B antigens. The RHESUS (Rh) system is another important blood type system, which is based on the presence of the Rh antigen. People with the Rh antigen are known as Rh-positive, while those without it are known as Rh-negative.