The iOS simulator lets you test your app on your Mac

The Simulator is a great tool for testing your apps quickly and for free. It doesn’t come with all the applications that a real device does, but for the most part, it behaves the same way. When you first start the simulator, you see the springboard—just like on a real iPhone (it’s the initial screen that shows all your app icons)—with iDecide installed (and a default icon that you can change later). Xcode then opens the app and your code is running.

There are some differences between using the Simulator and your iPhone. For starters, shaking and rotating your Mac won’t accomplish anything, so those don’t work in the Simulator. To approximate rotation and check landscape and portrait views, there are some commands under the Hardware menu. You also have limited gesture support, CPU and memory usage don’t represent reality, and hardware capabilities like tilt sensors (or the accelerometer or gyroscope) don’t exist at all.