We have three kinds of scratch available at our local farmer's co-op:
Scratch grains is cracked corn mixed with other grains and seeds. I feed this as a treat ONLY in the spring, summer and early fall.
Scratch is ground corn, looks like yellow cornmeal. I mix it with warm water to feed as a nightly treat in the wintertime.
Then we have what is known around here as Chops. Chops is chopped dry corn. I feed this in the wintertime too.
Most feed stores will have at least chops, but IMO it should be fed as a treat only and not make up more than 10% of the chickens daily diet.
They love it. It's chicken crack, but not nutritionally complete.