What is the difference between A+ and ARH+ blood group?

If you belong to the blood group A, you have A antigens on the surface of your red blood cells and B antibodies in your blood plasma.  A person with Rh- blood does not have Rh antibodies  in the blood plasma. However a person with Rh- blood can develop Rh antibodies if he or she receives blood from a person with Rh+ blood, whose Rh antigens can trigger the production of Rh antibodies.

With that in mind, ARH+ blood is one that has recieved the antibody from the Rh+ donor.