Complex sentence: The Shimmer Championship is a professional wrestling championship in Shimmer Women Athletes, and has also been defended on shows of sister promotions Ring of Honor and Full Impact Pro. Championship reigns are determined by professional wrestling matches, in which competitors are involved in scripted rivalries.
Split into simpler sentences: The Shimmer Championship is a professional wrestling championship in Shimmer Women Athletes. It is competed for in Shimmer Women Athletes, and has been defended on shows of sister promotions Ring of Honor and Full Impact Pro. Championship reigns are determined by professional wrestling matches, in which competitors are involved in scripted rivalries.