At the time of this writing, iOS devices are available in more than 90 different countries, and that number will continue to increase over time. You can now buy and use an iPhone on every continent except Antarctica. The iPad and iPod touch are also sold all over the world and are nearly as ubiquitous as the iPhone.
If you plan on releasing applications through the App Store, your potential market is considerably larger than just people in your own country who speak your own language. Fortunately, iOS has a robust localization architecture that lets you easily translate your application (or have it translated by others) into, not only multiple languages, but even into multiple dialects of the same language. ...