Personal experiences with the name Kiel: | Edit. My boyfriends name is Kiel pronounced Kyle because it is the name and spelling of a town in Germany that is a twin town to the one we live in Coventry.
A flapper is a rubber mechanism in your toilet tank that is the moving part of the flush valve, sealing water into the tank and allowing water to exit the tank when you flush. Flappers deteriorate over time as a result of in-tank cleaning products and chemicals used by utilities.
You would want to replace your flapper if it is leaking water from the tank, into the bowl. You would have determined this by use of a dye test (see this video on finding toilet leaks). A leaking flapper can waste hundreds of gallons of water over time, which is not good for your budget or water conservation.