One is a broad roller, like a mini-paint roller, except the roller is solid plastic. It has lines on it that as you roll them across a strip of dough, they reveal themselves to be patterned shapes on the dough. The patterns, sadly, don’t often go all the way through the dough, so afterwards you often having some fiddling to do, tracing them out with the tip of a knife. The shapes often get distorted as you try, Michelangelo-like, to free the shapes from the raw material surrounding them.
The other kind has a narrower roller on it, like a thick wheel. You snap actual Cookie Cutters onto the outer rim of the wheel, so that it’s vaguely reminiscent of one of those wheels with buckets on it designed to scoop up water for irrigation, with Cookie Cutter shapes in place of the buckets.