The Classic Tongue Twister Sea Sells Sea Shells by the Seashore is a good example of the difference between the "sh" sound and the "s" sound. In some languages there is no difference

This is an original work. Read it fast, the faster the better. Polly pleaded the polytheist to please let her pry the pretty purple polyester dress instead of Peony the pony, and the polytheist bedazzingly