Well, The rest of world's outlets are not compatible with our US plugs. You need a handy thing called an adapter.
We bought a universal one from Amazon for $5.00 and it's been invaluable. It's been on two International trips and worked just fine in both locations. I love this one because it's small, light weight, and in one piece. I also like this one because even though it doesn't actually have a slot for a 3 pronged grounded plug, it still has a dummy hole you can put it in, which makes it easier to find a compatible power bar to plug into it.
Have more than one device needing to be charged?
Bring a power bar with you so you can keep all your devices in one place, reducing the risk of leaving one behind during your adventures.