docs(guide/forms): clarify how NgModelController can be added to scope

Closes angular#5200

Author: wesleycho

Diff for: docs/content/guide/forms.ngdoc

@@ -115,9 +115,14 @@ This ensures that the user is not distracted with an error until after interacti
 
 A form is an instance of {@link api/ng.directive:form.FormController FormController}.
 The form instance can optionally be published into the scope using the `name` attribute.
-Similarly, control is an instance of {@link api/ng.directive:ngModel.NgModelController NgModelController}.
-The control instance can similarly be published into the form instance using the `name` attribute.
-This implies that the internal state of both the form and the control is available for binding in the view using the standard binding primitives.
+
+Similarly, an input control that has the {@link api.ng.directive:ng-model} directive holds an
+instance of {@link api/ng.directive:ngModel.NgModelController NgModelController}.
+Such a control instance can be published as a property of the form instance using the `name` attribute
+on the input control.  The name attribute specifies the name of the property on the form instance.
+
+This implies that the internal state of both the form and the control is available for binding in
+the view using the standard binding primitives.
 
 This allows us to extend the above example with these features: