It says this on the product page:
Free Fabric presets that alllow
you to change the cloth parameters
to simulate denim, cotton, wool
spandex, nylon and more (they work
like any other preset in Daz Studio)
I believe that these only change the cloth parameters as it says. It will not add a different fabric as such, but it will cause the ‘drape’ to take the weight and type of material into account.
This will only be useful I think, if you have the paid for Dynamic Clothing Control, but I could be wrong about that.