title: What is the (file) format of iOS/iPhone apps?
body: <p>I know that Android apps are packaged as *.apk files, but I have no idea in which way an iOS/iPhone app is stored?</p>
  
  <p>Assuming that iOS apps need to be developed and up- and downloaded to the apple App store I assume that the app is stored as a file. Which format does this file have?</p>