Our blood type refers to the antigens we have on our RBCs.
If we have A and B antigens on our RBCs, then our blood type will be AB. If we have only A or B or no antigens, then our blood type will be A or B or O respectively. Then there is also the Rh (D antigen) which is either present or absent on our RBCs. With that, for example, we are either AB+ or AB-. Everybody’s blood type is denoted by their ABO group and a + or – for the presence or absence of the Rh (i.e. D) antigen.
With blood donations, you have
PRBCs: Only red blood cells without plasma. This contains the donor’s antigens on their RBCs.
Plasma: This contains antibodies from the donor.
Platelets:
When dealing with PRBCs, you don’t want to give someone an antigen that they don’t have because that antigen will trigger their immune system to make antibodies that will destroy those antigens and at the same time make the patient very sick.