AC ratings are of EU standard intead of worldwide grade. It's no wonder that some salesmen outside of EU don't know the ratings. The ratings are for the grade of wear resistance. The performance of wear resistance is a key factor of
laminate flooring. You can find the details of ratings in detail at internet. Usually AC2 is suitable for home purpose and AC3 is suitable for commerical purpose. AC4 is for heavy commerical purpose.