The track element allows specifying explicit external timed text tracks for media elements. It does not represent anything on its own. Its provide a simple standardized way to add subtitles, captions, screen descriptions and chapters to video and audio.
You can also use this for time metadata. The source data for each track is a text file made up of a list of cues, and cues can include data in formats such as JSON or CSV. This is extremely powerful, enabling deep linking and media navigation via text search.
The track element is currently available in Internet Explorer 10 and Google Chrome. Firefox support is not yet implemented.