Diagetic VS Non Diagetic Sound

What is the difference between diegetic and non diegetic sound? What is an example of each that you can think of from a film?

Diagetic sound refers to a "source [that] is visible or implied in the world of film." It an be either on screen on off screen as long as the sound is literal. These include the actors' dialog, sound created from an object such as a smashing of a window, and orchestral sound. On the other hand, non-diagetic sound refers to a "source [that] is not present or implied in the narrative universe." Non diagetic sound is often used as a commentary or tool to arouse emotion. These include music, narration, and extra sound included for effect.