Document states and visibilities of content.

api/docs/concepts.md

@@ -15,6 +15,24 @@ is a CMS that can manage multiple sites and endpoints.  The key concepts to unde
 Content is some sort of information, that is part of a site.  There are different kinds of content that can
 be managed by a user, and can be linked to other pieces of content.
 
+Content can be in any of these four states:
+
+- Draft
+- Scheduled
+- Published
+- Archived
+
+Content can also deleted completely out of the system.
+
+Content also has the following visibilities:
+
+- Public
+    - Viewable to anyone.
+- Subscription
+    - Viewable to subscribers and above.
+- Private
+    - Viewable only to the individual writer, editor or admin.
+
 ## Site
 
 A site is any collection of content that is related.  A site maybe an instance of a website or a content for