http://www.apple.com/quicktime/pro/tutorials.html
Each track represents a unique aspect or ability that you can change over time. A single movie may have many different track types, including video, audio, text, sprite, Flash, HREF, hinting, QuickTime VR, and chapter divisions. Each track, in turn, may possess many modifiable properties.
http://www.apple.com/quicktime/tutorials/hreftracks.html
An HREF track is a text track that adds
interactivity to a QuickTime movie, and contain URLs ...
with examples: http://web.uvic.ca/akeller/pw408/d_qt_link_to_web_pages.html
http://www.apple.com/quicktime/technologies/interactivity/
Creates alternate movies for various internet connection speeds, CPUs, languages, and more. This version runs on Mac OS X and allows you to create a reference movie that supports QuickTime 6/7.
http://developer.apple.com/quicktime/quicktimeintro/tools/
Can creare a playlist of movies: http://www.qtbridge.com/pageot/qtnext/Sequence_eng.html, other tools are also available.