There are actually quite some scriprs and threads about Track Chunk,
it is just a way to get ALL the tracks infos and its items in a string format for quick search/replace/manipulation, if more regular reascript API function doesnt exists or would be too slows for some reason.
It is well documented:
https://github.com/ReaTeam/Doc/blob/...%20Definitions
Take inspiration from existing scriprs shared via reapack for eg.
The question is more... what are you trying to achieve ?