It is a small passport-like booklet issued by the American Automobile Association (AAA) and is either recommended or required by more than 150 countries - essentially everywhere but English-speaking nations. Some countries say it's the law for non-native drivers to have one, while others simply recommend it to help break down communication barriers during travel. The permit translates your American driver's license into ten languages, which helps with the language barrier if an accident should occur. If you do not have one, whether your vacation will end or not will depends on the country. In Japan you may be arrested and deported if you don't have the necessary paperwork. In general, the car rental agent will ask to see it if you're travelling outside of Europe since Europe no longer requires one. The most important thing you should do is find out if your travel destination requires one or not long before you leave. To get one, visit your local AAA and bring two passport sized photos and $20. The whole process can take up to six weeks.