documented new tag behaviour

docsite/rst/playbooks_tags.rst

 Tags
 ====
 
-If you have a large playbook it may become useful to be able to run a 
-specific part of the configuration without running the whole playbook.  
+If you have a large playbook it may become useful to be able to run a
+specific part of the configuration without running the whole playbook.
 
 Both plays and tasks support a "tags:" attribute for this reason.
 
@@ -24,7 +24,7 @@ Example::
 If you wanted to just run the "configuration" and "packages" part of a very long playbook, you could do this::
 
     ansible-playbook example.yml --tags "configuration,packages"
-    
+
 On the other hand, if you want to run a playbook *without* certain tasks, you could do this::
 
     ansible-playbook example.yml --skip-tags "notification"
@@ -40,6 +40,28 @@ And you may also tag basic include statements::
 
 Both of these have the function of tagging every single task inside the include statement.
 
+
+Special Tags
+````````````
+
+There is a special 'always' tag that will always run a task, unless specifically skipped (--skip-tags always)
+
+Example::
+
+    tasks:
+
+        - debug: msg="Always runs"
+          tags:
+            - always
+
+        - debug: msg="runs when you use tag1"
+          tags:
+            - tag1
+
+There are another 3 special keywords for tags, 'tagged', 'untagged' and 'all', which run only tagged, only untagged
+and all tasks respectively. By default ansible runs as if --tags all had been specified.
+
+
 .. seealso::
 
    :doc:`playbooks`