Specifically, the details will be provided on:
- the structure of C aspect records;
- the way L and D aspects are recorded in respect to the operation of the language fallback mechanism;
- the exact difference between the S and T records;
- the contexts in which O is recorded.
The existing documentation from the above mentioned locations, plus the new details are provided in the new central Usage Tracking documentation: https://doc.wikimedia.org/Wikibase/master/php/md_docs_topics_usagetracking.html