Well, this FAQ contains about the best (and only) explanation of why the Light edition and what is not in it:http://www.linuxmint.com/faq.php
And anything not installed in the Light edition by default can be added back in by the end user.
To be perfectly frank, and meaning no offense, I am trying to understand why it is so important to know what each and every bloody codec does? As I am sure you know, each one decodes a given audio/video file format. If you looked at the links for W32codecs & Gstreamer I shared, so many of the codecs listed are corner cases that most average users (me for sure, perhaps you?) will never see nor use in our lifetimes.
Is there a particular use case you need? Have you run across a audio/video file you have that Mint cannot play?