Digital audio refers to representing sound numerically by decomposing analogue sound waves into samples. This differs from analogue media like tapes which store sound physically. Interactive features in digital publications allow two-way communication through responding to user instructions like pausing or rewinding. They present content through text, images, animation and video. Video provides a visual aid but can be poor quality or digressive. Graphics also offer visual aids through images, color and identity, but some graphics may not aid understanding.