Sheet music
A  score  is printed music of a piece written for several instruments. The music (parts) for each instrument are written above one another on separate staves.  A conductor can see from the score what each instrument should be playing and how it fits together.  Each player only has his or her own part (the notes that that performer plays) in front of him/her.  From time to time, if the instrument has long period where he/she does not play (that is, has a block of rests), the publisher may print, usually in smaller type, a portion of the music another instruments (usually an instrument playing the melody) would be playing to help the performer know what to listen before he/she starts playing.  These smaller notes are called cues because it cues, or clues, the performer that he/she is going to start playing soon.)