In short, VIPER (View Interactor Presenter Entity Router) is an architecture which aims at solving the common Massive View Controller problem in iOS apps. When implemented to its full extent, it achieves separation of concerns between modules in your code, which yields testability. This is also good because poor testability is another problem with Apple's Model View Controller architecture.

If you're interested in learning more about how it works and how you can easily generate necessary VIPER files, check out the README for our VIPER Xcode Templates GitHub repo.