Updated a few doc paragraphs following the app-loading refactor.

docs/internals/contributing/writing-code/unit-tests.txt

@@ -222,7 +222,6 @@ Tests for contrib apps go in their respective directories under
 ``django/contrib``, in a ``tests.py`` file. You can split the tests over
 multiple modules by using a ``tests`` directory in the normal Python way.
 
-For the tests to be found, a ``models.py`` file must exist, even if it's empty.
 If you have URLs that need to be mapped, put them in ``tests/urls.py``.
 
 To run tests for just one contrib app (e.g. ``auth``), use the same

docs/intro/reusable-apps.txt

@@ -42,9 +42,10 @@ projects and ready to publish for others to install and use.
     bar``. For a directory (like ``polls``) to form a package, it must contain
     a special file ``__init__.py``, even if this file is empty.
 
-    A Django *app* is just a Python package that is specifically intended for
-    use in a Django project. An app may also use common Django conventions,
-    such as having a ``models.py`` file.
+    A Django *application* is just a Python package that is specifically
+    intended for use in a Django project. An application may use common Django
+    conventions, such as having ``models``, ``tests``, ``urls``, and ``views``
+    submodules.
 
     Later on we use the term *packaging* to describe the process of making a
     Python package easy for others to install. It can be a little confusing, we
@@ -128,11 +129,10 @@ this. For a small app like polls, this process isn't too difficult.
        This helps others looking for Django apps identify your app as Django
        specific.
 
-       The application names (that is, the final dotted part of the
-       path to the module containing ``models.py``) defined in
-       :setting:`INSTALLED_APPS` *must* be unique. Avoid using the
-       same name as any of the Django :doc:`contrib packages
-       </ref/contrib/index>`, for example ``auth``, ``admin`` or
+       Application labels (that is, the final part of the dotted path to
+       application packages) *must* be unique in :setting:`INSTALLED_APPS`.
+       Avoid using the same label as any of the Django :doc:`contrib packages
+       </ref/contrib/index>`, for example ``auth``, ``admin``, or
        ``messages``.
 
 2. Move the ``polls`` directory into the ``django-polls`` directory.

docs/ref/settings.txt

@@ -1285,18 +1285,17 @@ INSTALLED_APPS
 
 Default: ``()`` (Empty tuple)
 
-A tuple of strings designating all applications that are enabled in this Django
-installation. Each string should be a full Python path to a Python package that
-contains a Django application, as created by :djadmin:`django-admin.py startapp
-<startapp>`.
-
-.. admonition:: App names must be unique
-
-    The application names (that is, the final dotted part of the
-    path to the module containing ``models.py``) defined in
-    :setting:`INSTALLED_APPS` *must* be unique. For example, you can't
-    include both ``django.contrib.auth`` and ``myproject.auth`` in
-    INSTALLED_APPS.
+A tuple of strings designating all applications that are enabled in this
+Django installation. Each string should be a full Python path to an
+application configuration class or to a Python package containing a
+application. :ref:` Learn more about applications </ref/applications>`.
+
+.. admonition:: Application labels must be unique
+
+    Application labels (that is, the final part of the dotted path to
+    application packages) *must* be unique in :setting:`INSTALLED_APPS`.
+    For example, you can't include both ``django.contrib.auth`` and
+    ``myproject.auth``.
 
 .. setting:: INTERNAL_IPS