"I like to eat, but you eat my meal."
Translation:J'aime manger, or tu manges mon repas.
I was wondering that, too. There was a similar situation in German, where a less common word ("mitunter") was taught before/instead of a more common one ("manchmal.") Beginning learners will assume they're learning natural (not formal or "fancy") language, unless you clue them in.
It's probably like "yet" in English. Duolingo should probably distinguish between when it's teaching you formal and informal words. If I wasn't also in French class, I would have no idea the difference between tu and vous.
What is the difference between "J'aime manger, or tu manges mon repas," "J'aime manger, donc tu manges mon repas," and "J'aime manger, or vous mangez mon repas," aside from the difference between vous and tu?
I think "donc" is more like "thus/therefore" ("Je pense, donc je suis.")
I just looked up "or"; the first meaning is "gold" of course, but the 2nd: 2(a) now; as it happens, in fact (rare); "or donc"=thus, therefore So, there's also "or donc"! But "or" by itself is rare, according to this dictionary.