A travel plug adapter simply adapts your plug fit the different shapes of international outlets, whereas voltage converters actually control the voltage flowing into your device. Plug types A and B are found in the USA, Japan, Taiwan, South and Central America, and the Caribbean, but you'll need an adapter to fit an A or B plug into any of the other outlet types. Because voltage standards vary around the world, you may sometimes need both a plug adapter and voltage converter: The yellow shaded areas of the voltage map are 100-127 volts, but you can see that much of the rest of the world, including Europe, Africa, and Australia, is shaded blue for 220-240 voltage. If you're from a yellow shaded country, AND your device isn't dual voltage (see more info below), you'll need a voltage converter to avoid frying your electronics. Check the map for exceptions like Canada and Japan, but frequent travel will eventually land you in a country with higher voltage. A very detailed breakdown of plug types and voltage by country is available on Wikipedia, and see the bottom of this article for more info on plug types and corresponding countries.