OE or "Open End" spun cotton are shorter cotton fibers spun to produce a nice yarn but usually is not as soft or strong as Ring-Spun cotton. Items woven with OE cotton will sometimes "track," which appears after the woven item has been washed and dried. Tracking looks as if a pattern has been woven when only tabby or plain weave was treadled....very pretty and interesting results!
RS or "Ring Spun" cotton are longer cotton fibers spun to produce a softer & stronger yarn than OE spun cotton. It has a slight "sheen" to it. It does not track when woven in tabby weave like OE cotton does. It is softer to the touch and has more drape than OE cotton.