Back-focus or Front-focus is something that existed since auto-focus (AF) was introduced.
Referring that lens has a Back-focus or Front-focus problem is when focus point acquired by AF is constantly (in every photo) behind or in front of actual focusing point.
Different lenses on same body will not behave in same way most of them will be right on the spot but some might front-focus and other may back-focus.
In most new high end cameras there is setup option to correct this problem. For older and low end cameras you can always send them to service center for tune-up. (bare in mind that this will correct AF problem with your lens and camera combo but if you sell lens or upgrade camera body problem will reappear because lens was tuned to your old body)