Metadata - (Sometimes known as Side Information) - (1) Information about the audio and/or video data that’s included in the signal's data stream. It might be considered data about the data itself.  Metadata can aid in providing Interactivity. Also see Essence. (2) Information downloaded over the Internet that helps you sort through and selectively view or listen to just the good parts of your previously recorded and stored broadcasts. http://en.wikipedia.org/wiki/Metadata

Ancillary Data – Underlying, subordinate, secondary or subservient data. It might, depending on the situation, be associated with Metadata.