Django's introductory tutorials take a simplified approach to getting up and running on the platform. They introduce the concept of a Django project using django-admin.py and the startproject command. This is the easiest way to get going, but it hides a significant amount of activity that goes on under-the-hood. For the project that we will build throughout this book, we will take a more sophisticated approach, by thinking of our Django projects as a collection of normal, plain Python modules. Django calls these modules "apps."
In some ways the term "app" is unfortunate because it hints at something large, a full-blown application. But in Django, apps are usually small and simple. Properly designed apps can be plugged together to form powerful combinations, with each app solving its own portion of a larger problem.
Apps, like any good Python module, encapsulate a specific set of functionality; this is usually by focusing on a small problem and solving it. This is actually a well-established pattern of software design, originating in the UNIX operating system. Past and current versions of UNIX provided numerous tiny programs that solved a simple problem: pattern matching with grep, word counting with wc, and so on.
By emphasizing this approach in our projects, we can take full advantage of Django's rapid development philosophy. It will lead to better code and cleaner designs.