Most American-made electrical appliances work at 110 volts. Japan, most of North America, parts of South America, and the Caribbean use voltage between 100 and 125. The rest of the world uses 220 – 240 volts. Check before you start packing.
Also, check the label on your appliance before buying a converter, as it might be designed to work at both 110/120 and 220/240 volts. Many of the newer items do, especially those designed for travel. If so, you’ll probably only need a plug adapter. If your appliance only operates at 110 volts, you’ll need to buy a voltage converter.
Even if two countries operate on the same voltage, their outlets might not take the same shape of plug…which is why you need an adapter. An adapter will allow you only to plug your appliance into another type of outlet, but not change the electrical voltage.
Travel stores often sell convenient and inexpensive kits with five different-sized adapters that will work with nearly any outlet in the world. Note that these often won’t work for appliances that need to be grounded, which will require a more expensive grounding adapter.