An international power supply is the device which means it doesn't matter what country you're in, or even if you know what country you're in (more of a problem than you might suspect) - you just plug your Mac in and it figures it out for itself. We call this principle Plug and Play. Or at least, Microsoft calls it that because it hasn't got it yet. In the Mac world we've had it for so long we didn't even think of giving it a name.