I don't know the official definition of the term, but I've always thought it was someone born in 1995 or later, where they never lived in a world without online services like AOL, and later Google, Facebook, etc.... Where they never lived in a world that existed before the World Wide Web. Where they never lived in a world without being able to access data online through something at least as fast as a 56k baud modem. Where they never lived in a world without cellphones and portable home phones.
They may not have had all these things themselves, but they knew people who did.
And this future is also unevenly distributed, of course.
Especially in the context of who the target audience is (in marketing, when thinking about UX and so on - the prototypical agency/consultants/client talk intermixed with a lot of BS and important sounding words).
So no idea if it is in general use here, though.
I'm French speaking as well. It's indeed surprising; I thought this would be understood by everyone ;-)