For the FAA, the breakdown is Catagory, Class and Type
Catagory is Airplane, Rotorcraft-Helicopter, multi-engine glider (
Class is Single engine land, etc. All helicopters below 12,500 lbs MGW are of the same class.
Type is the broad model designation, generally, like SK-76 or SK-61. A model designation Type Board meets for all newly certified helicopters, chaired by the Flight Standards guys to decide if the unique aspects of that machine require that it be controlled by having a separate type rating. This board also decides how broad the model type designation is - in other words, they decide if the D model is so different that it must be typed differently than the A model.
Note that Pt 135 operations require type ratings for everything, so a new type is designated for 135 pilots, even if the base model helo does not specifically need a type rating. I know of no helo below 12,500 that deserves its own type, except for 135 pilots.
The distinction is generally that currency is met in the same catagory and class machine.