The adapter Type C is the most common adapter Type used in the following countries: Europe (Bosnia, Bulgaria, Croatia, Greece, Hungary, Iceland, Latvia, Lithuania, Portugal, Romania, Russia, Serbia, Slovenia, Spain, Turkey, Ukraine) South America (Bolivia, Brazil, Chile, Peru) Asia (Thailand, Indonesia).
It isn't just the voltage that's different in Europe. The wall outlets and sockets are also shaped differently, and can't accommodate American AC wall adapters or chargers without the right kind of adapter. For travel to Europe, you can find superior quality adapters for 110-to-220V at very reasonable prices.