The difference between a nylon zipper and a plastic zipper is that the teeth of the nylon zipper are thinner and look translucent. It feels like the loops of plastic threads.
Plastic zipper - resin zipper, teeth thick, opaque. It feels like a piece of plastic, usually square.
Nylon zipper is soft, resin zipper is more stiff.
General underwear, skirts and other thin fabrics and sweaters with nylon zippers more.
The jacket is zipped with resin.
Jeans with metal zipper for leather.