Diegetic Sound: Sound that originates from within the video or film's world is termed diegetic sound. It can come either from on-screen or off-screen but it always happens at the same time the action takes place.
Non-Diegetic Sound: Sometimes called commentary or non-literal sound, the non-diegetic sound is any type of sound that does not specifically exist within the world of the film itself. In other words, it's the type of sound that characters in a movie cannot hear, but that we can.
Baby Driver - https://www.youtube.com/watch?v=7ARFyrM6gVs
Baby Driver uses both non-diegetic sound and diegetic sound as the character can hear the music through his earphones, making it diegetic sound as the action is also taking place.
Non-Diegetic sound is also being used as we can also hear the music being played but we can also hear the outside word sounds when he will struggle hearing this with these earphones in with music making it hard for him to hear.
