The Anki apkg format is a zip file containing two SQLite databases and media files.
- What is in the two SQLite databases?
- How are the media files identified / referenced?
Of further interest:
How do I "pack" and "unpack" (or "dump" / "load") Anki apkg files, i.e. put the whole content (including what is in the SQLite dbs) into the filesystem folder structure.