Upvote:1
Interrail passes can only be bought by European residents. Eurail Passes by non residents. Citizenship actually does not matter, as eg. a French resident of the US can buy a Eurail Pass. It is where you live that matters, not what your nationality is.
But the other major difference is that the Interrail pass only gives you unlimited travel outside your own country. It is not valid in your own country of residence except for two trips, which have to be for the purpose of leaving (or entering) your country.