What is the difference between a Django project and an app?

I avoid treating 'reusable app' as a requirement for every internal feature. Some apps are deliberately product-specific, and splitting them too early creates circular imports and awkward cross-app transactions. When apps interact, I prefer explicit service or query boundaries and stable model references over importing internals everywhere. The registry solves framework discovery; it is not a dependency container or a reason to hide runtime work during import.