IPhone applications are written with XCode and IOS SDK. The apps are written with the building blocks provided by the framework. The language is Objective C. Creating a hello world application with a one page is easy because you choose the templates, pick the controls and write the associated controller logic. You can test the app in the simulator that comes with XCode.
Publishing an app is also easy using the following steps. Apps are published through the App store. You provide the app and the digital certificates. The App is then compiled and submitted to the App Store. You need the following : identity which is a unique id for an app, a distribution certificate and a private key  that is generated in the app store, a distribution provisioning profile, icons and loading screens.