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...similar to mercerized cotton. 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.