There are 4 different blood types (A, B, O, & AB). Each blood type can either be Rh positive or Rh negative. (e.g., A+, A-, B+, B-, O+, O-, AB+, AB-).
Blood type AB is the universal receiver when it comes to donating blood. That means anyone can donate blood to a person with AB blood.
Blood type O is the universal donor, which means that anyone can take O blood. '
All other blood types can only be donated to their specific blood type (i.e. A-A, B-B.)
A B AB O, each of which can be positive or negative, for a total of eight.