[I'm not sure this is the best place for this kind of question, but I couldn't identify anything better. Please do redirect me if appropriate!]

In the course of engaging in EC261 pedantry, I've discovered that there are not only operating carriers and marketing carriers, but also ticketing carriers.

Operating and marketing carrier I can understand in terms of being "whose actual plane are you flying in" (though I know there are some corner cases with things like "wet/dry/damp lease/ACMI" that I don't really know about) and "whose airline code appears on your ticket" respectively, but what is the ticketing carrier? When will it differ from the marketing carrier, how will I know, and what is the significance if it differs? (My understanding is that for EC261 it's the operating carrier that matters, so marketing v ticketing maybe not relevant, but there might be other impacts?)