I keep seeing ITUNESADVISORY misused as a tag so I thought it was worth a post to share my view:
Most services (that are not apple) use a boolean tag to flag tracks with explicit lyrics. Usually a 0 for not explicit and a 1 for explicit.
ITUNESADVISORY adds additional flags, most notably, it adds a 2, for "cleaned" or "censored" tracks. This is a specific subset of not explicit. Services that use a boolean tag would simply flag this type of track as not explicit. While that is accurate, given the context, it is not accurate in the context of ITUNESADVISORY. In other words mapping an explicit t/f flag to ITUNESADVISORY often misrepresents the data, imo since there is not enough data available to map it correctly.