Most likely no difference whatsoever. It is marketing - similar to "digital" tripods. Although if it reflects the fact that the product was introduced after digital became mainstream, you at least know that it is a recent product.
The "circular" part may matter, because circular polarizers are compatible with more auto-focus systems than linear polarizers are.
Even if your film camera doesn't offer auto-focus you may still need a circular polarizer, because some metering systems that use beam splitters also require circular polarizers.