Definition of "Exposition" :
noun: (music) the section of a movement (especially in sonata form) where the major musical themes first occur
noun: an account that sets forth the meaning or intent of a writing or discourse
"We would have understood the play better if there had been some initial exposition of the background."
noun: a systematic interpretation or explanation (usually written) of a specific topic
noun: a collection of things (goods or works of art etc.) for public display