Original: Guys and Dolls is a musical, with the music and lyrics written by Frank Loesser and book by Jo Swerling and Abe Burrows, based on "The Idyll of Miss Sarah Brown" and "Blood Pressure", two short stories by Damon Runyon.
Simplified: The music and lyrics were written by Frank Loesser, and the speaking parts were written by Jo Swerling and Abe Burrows. The story of Guys and Dolls is based on short stories written by Damon Runyon.