A cue sheet is a document which is filed with the performing rights societies and contains a detailed listing of each piece of music used in a film or television production.
The cue sheet is usually prepared by the music editor for a production, but can also be prepared by the composer if the composer has information on all music used in the production.
The cue sheet contains information for each piece of music including the writer(s), publisher(s), usage of the music (background, theme, etc.), length of the music, and a title for each piece of music.
The ASCAP site has a great article including an example of a cue sheet located here.