The small intestine is called small because the diameter or the width of the tube is much less than the large intestine. The parts of the small intestine include the duodenum, jejunum and the ileum. The duodenum is a segment of intestine between the stomach and the jejunum that is very active in digestion where many different enzymes mix from the stomach, liver, gallbladder and pancreas. The small intestine is the location in the body where the majority of the nutrients from ingested food ...
CLR is a common household cleaner that is designed to clean the heavy duty stains of rust, calcium, and lime. Usually these stains are caused by water build up and the constant drip of minerals in the water.
It is basically Hydrochloric acid that IMMEDIATELY eats away the hard water deposits (that's what the ring is, by the way, and CLR is not powerful enough to dissolve it).  You pour the sizzle into the overflow tube inside your toilet tank (the tube sticking out of the water), and it will flow down inside the bowl.