Blood types of the AB0 system
Red blood cells carry different kinds of proteins on their membranes.
The most common ones are protein A and protein B
If you have blood type A, your red blood cells only carry protein A
If you have blood type B, your red blood cells only carry protein B
If you have blood type AB, your red blood cells both carry protein A and B
if you have blood type 0 (zero), your red blood cells carry neither