Sound Types

Diagetic Sound - Diagetic sounds are part of the film world we are watching. This could be birds singing in a tree, someone talking or a song playing of the radio in the background.
Non-Diagetic Sound - This kind of sound is not recognised as part of the film world and include backing music that is not coming from a clear source or a voice-over which narrates part of the movie e.g. JD from Scrubs internal commentary on his day to day activities.
Sound Bridges - A sound bridge is when the sound from one scene will carry other to the next making the change seem more seamless and smooth, instead of being disjointed and sudden e.g. the whistle of a boiling kettle brdiges with the horn of a train.
Parallel Sound - Parallel sounds are the kinds of noises we expect to see in a scene. For example, if you are watching children playing happily on a beach, you would expect to hear laughter, kids talking etc.
Contrapuntal Sound - This kind of sound is the opposite of parallel sound. This is when you hear noises which do not fit in with the scene you are watching. A good example of this is the scene from 'Jaws' when people are having a good time on the beach, but instead of hearing the expected sounds of laughter, a sinister and dark music is playing telling you something bad is about to happen.