Director Commentary

A directors commentary is typically made for bonus features of a DVD. It is often made as a commentary over the whole feature, but sometimes just certain scenes.
 A commentary can contain more than one speaker. For example, directors are often accompanied by the actors from the film, or the producer.
Audio commentary's allow the audience to find out extra information they may find interesting about the film, that they might not have otherwise been able to find out.
 The directors commentary's can be more personal to the audience as it can feel like the director is talking directly to them.