What does blood type A positive mean?

Type A blood means that on the outer cell membrane there is an antigen that identifies the cell as being "Type A".

If you have "positive" blood, this means you have tested positive for the Rh factor, and there is an antigen identifying the Rh factor on the outer cell membrane. If you are Rh negative, there is no antigen on the outer membrane.

The ABO and Rh blood types are just 2 of the 32 blood-type components of the red blood cell.