The iPhone SDK provides the tools and resources needed to create native iPhone applications that appear as icons on the user’s Home screen. Unlike a web application, which runs in Safari, a native application runs directly as a standalone executable on an iPhone OS–based device. Native applications have access to all the features that make the iPhone and iPod touch interesting, such as the accelerometers, location service, and Multi-Touch interface. They can also save data to the local file system and even communicate with other installed applications through custom URL schemes.

In iPhone OS, you develop native applications using the UIKit framework. This framework provides fundamental infrastructure and default behavior that makes it possible to create a functional application in a matter of minutes. Even though the UIKit framework (and other frameworks on the system) provide a significant amount of default behavior, they also provide hooks that you can use to customize and extend that behavior.