The contrib
packages are a part of Django that contain some very useful applications that the Django developers decided should be shipped with Django. The included applications provide an impressive set of features, including some that we'll be using in this application:
Admin is a full featured CMS that can be used to manage the content of a Django site. The Admin application is an important reason for the popularity of Django. We'll use this to provide an interface for site administrators to moderate and manage the data in our application
Auth provides user registration and authentication without requiring us to do any work. We'll be using this module to allow users to sign up, sign in, and manage their profiles in our application
Note
There are a lot more goodies in the contrib
module. I suggest you take a look at the complete list at https://docs.djangoproject.com/en/stable/ref/contrib/#contrib-packages.
I usually end up using at least three of the contrib
packages in all my Django projects. They provide often-required features like user registration and management, and free you to work on the core parts of your project, providing a solid foundation to build upon.