Xcode is Apple's Integrated Development Environment (IDE) for developing for both iOS and Mac OS X. In other words, most of what you will need in order to develop software for the Mac or iOS devices is integrated into one nice, clean application. When you install Xcode on your Mac, you get everything needed to develop for both the Mac and iOS devices. The IDE takes everything from your program and puts it all together into a single executable application; this is referred to as compiling. If you are compiling on your Mac or the iOS simulator, you can run your application once everything is compiled. However, it gets a bit more complicated when compiling for iOS devices, but we will run through that later.