Django uses apps to divide projects into manageable and reusable chunks. All examples in tutorials use polls or articles in unrelatable circumstances. In a modern example like Reddit (or even Amazon or Ebay), how would Django apps be used to break up the website?
“App” is a particularly odd term for this concept, specific to Django. Consider this quote from the documentation:
It is important to understand that a Django application is just a set of code that interacts with various parts of the framework. There’s no such thing as an Application object. However, there’s a few places where Django needs to interact with installed applications, mainly for configuration and also for introspection. That’s why the application registry maintains metadata in an AppConfig instance for each installed application.
This means, basically, that an app is simply a module with a certain amount of special, framework-conferred status (in terms of configuration and introspection). In practice, this is often used for aspects of the project that are conceptually distinct—an example, in Reddit, might be ads. It’s difficult to identify anything else without seeing their code base; most of the rest of the site’s functionality is based on your user account, which, in Django terms, would be a shared model, and thus would preclude the idiomatic use of Django apps.