Development for iOS is similar to Desktop to some extent. It is the same language (Xojo), the same way of handling events and you have access to the same classes (except those specific to Desktop).
Since the move to Xojo API2 for iOS, most code can be copy-pasted from Desktop to iOS
There are some differences such as handling the UI, Windows are called Screens and you can’t have several screens show up at the same time (on iPhone at least).