Merge intro into index

Author: stevepiercy

docs/backend/content-types/index.md

@@ -1,17 +1,82 @@
 ---
 myst:
   html_meta:
-    "description": "Dexterity content type overview."
-    "property=og:description": "Dexterity content type overview."
-    "property=og:title": "Content Types"
-    "keywords": "Content Types, Dexterity"
+    "description": "How to develop Dexterity content types in Plone."
+    "property=og:description": "How to develop Dexterity content types in Plone."
+    "property=og:title": "Content types"
+    "keywords": "Content types, Dexterity, Plone"
 ---
 
 # Content Types
 
+This part of the documentation describes how to develop content types in Plone.
+Content types are implemented through the {term}`Dexterity` framework.
+
+
+## What is a content type?
+
+Each item in a Plone site is an instance of a particular content type.
+We have different content types to reflect the different kinds of information about which we need to collect and display information.
+
+`Folder`, `Page`, `News item`, `Event`, `File` (binary), and `Image` are examples of content types.
+
+Lots of things in Plone can be configured to work differently based on the content type.
+For example, each content type has:
+
+-   a {doc}`schema </backend/schemas>` specifying the fields which can be edited for the content type
+-   a list of {doc}`behaviors </backend/behaviors>` which supply additional functionality that can be attached to the content types for which the behavior is enabled
+-   a {doc}`workflow </backend/workflows>` controling transitions between publishing states and associated permissions
+-   a version policy controling whether to store a revision history
+
+It is common in developing a website that you'll need customized versions of common content types, or perhaps even entirely new types.
+
+
+## Designing with content types
+
+Plone uses the ZODB, an object database, instead of a relational database as its default content store.
+The ZODB is well suited to heterogeneous, loosely structured content such as web pages.
+
+Types in Plone are either `containers` or `items` (this distinction is sometimes called folderish versus non-folderish).
+A one-to-many type relationship is typically modeled as a container (the "one") containing many items (the "many"), although it is also possible to use references across the content hierarchy.
+
+Each type has a {doc}`schema </backend/schemas>`, which is a set of {doc}`/backend/fields` with related properties, such as a title, default value, constraints, and so on.
+The schema is used to generate forms and describe instances of the type.
+In addition to schema-driven forms, a type typically comes with one or more {doc}`/classic-ui/views` as well as {doc}`/classic-ui/viewlets` and is subject to security—for example, add permissions, or per-field read and write permissions—and workflow.
+
+
+## Topics
+
+This part of the documentation will cover the following topics.
+
+-   Some basic design techniques for solving problems with content types in Plone
+-   Setting up a Dexterity development environment
+-   Creating a package to house your types
+-   Building a custom type based on a schema
+-   Creating custom views and forms for your type
+-   Advanced customization, including workflow and security
+-   Testing your types
+-   A quick reference to common fields, widgets, and APIs
+
+```{seealso}
+See the chapter {doc}`training:mastering-plone/dexterity` from the Mastering Plone 6 Training for a step-by-step tutorial to create a custom content type.
+```
+
+
 ```{toctree}
 :maxdepth: 2
-intro
+:caption: Table of contents
 creating-content-types
 fti
-```
+```
+
+```{toctree}
+:maxdepth: 2
+```
+% Uncomment each of the following and move into the toctree above when migrated from Plone 5 documentation
+% prerequisite
+% schema-driven-types
+% model-driven-types
+% custom-views
+% advanced/index
+% testing/index
+% reference/index