Roughout or Smoothout:
This determines which side of the leather faces the outside of the holsters. Roughout adds some extra grip to hold the holster in place. Smootout tends to make it easier to get the holster on and off.
Adds a thinner piece of leather to the inside of the holster with the smooth side facing in. This helps protect the finish on your gun by reducing the chance of dirt and grit getting caught up inside the holster.