Fill in Overview, re-use parts of the updated Products.CMFPlone README, work in progress

Author: fredvd

docs/overview/index.md

@@ -20,17 +20,85 @@ This page needs content.
 
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-## Key concepts of Plone
+## Overview
+
+Plone is a mature, secure, and user-friendly content management system (CMS).
+Plone was first released to the public on October 4, 2001.
+
+Plone has the maturity, stability, and reliability of an application maintained by open source developers with decades of experience, while continually evolving and adapting to modern technology.
+
+Lots of customizations can be made trough-the-web, such as creating content types, themes, workflows, and much more.
+A full filesystem based development workflow is also possible.
+Plone may be extended and used as a framework on which to build custom CMS-like solutions.
+
+Plone works as a:
+
+- Full-featured server-side rendered HTML CMS.
+- React-based frontend for editing and viewing content, backed by a server with a REST API.
+- Headless CMS server with a REST API, allowing a developer to build a custom frontend with their chosen technology.
+
+
 
 
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-### Web content management system
+## Key benefits
+
+Security is built into Plone's architecture from the ground up.
+Plone offers fine-grained permission control over content and actions.
+
+Plone is easy to set up compared to other CMS'es in its category, extremely flexible, and provides you with a system for managing web content that is ideal for project groups, communities, websites, extranets, and intranets.
+
+- **Plone empowers content editors and web application developers.**
+  The Plone Team includes usability experts who have made Plone easy and attractive for content managers to add, update, and maintain content.
+
+- **Plone is international.**
+  The Plone interface has more than 35 translations, and tools exist for managing multilingual content.
+
+- **Plone follows standards and is inclusive.**
+  Plone carefully follows standards for usability and accessibility.
+  Plone is compliant with WCAG 2.1 level AA and aims for ATAG 2.0 level AA.
+
+- **Plone is open source.**
+  Plone is licensed under the GNU General Public License, the same license used by Linux.
+  This gives you the right to use Plone without a license fee, and to improve upon the product.
+
+- **Plone is supported.**
+  There are over two hundred active developers in the Plone Development Team around the world, and a multitude of companies that specialize in Plone development and support.
+
+- **Plone is extensible.**
+  There is a multitude of add-on products for Plone to add new features and content types.
+  In addition, Plone can be scripted using web standard solutions and open source languages.
+
+- **Plone is technology neutral.**
+  Plone can interoperate with most relational database systems—both open source and commercial—and runs on a vast array of
+  platforms, including Linux, Windows, macOS, and BSD.
+
 
 
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-### Add-ons
+## High Level Overview
+
+Plone is a content management platform with its backend written in Python. The backend builds upon Zope, an open source web 
+application server and development system, and thus on the pluggable Zope Component Architecture (ZCA). The frontend has up until now
+served HTML based content, with advanced resource management on the server to add and bundle CSS and javascript. 
+
+With the release of Plone 6 there are now two out of the box supported configurations possible for a new Plone website.
+
+You can still use the Python based backend server to render the content server side and deliver html to the browser.
+This setup is referred to in the documentation as 'Classic UI' and has been supported by Plone since its release. 
+For container based deployment you only need the plone-backend image, or a derivation with your customisations added. 
+
+The default and advised configuration for new websites in Plone is to use our new React Based javascript frontend called 'Volto'.
+For this setup you will still need to run the Python based backend server, but with the REST API enabled and an updated configuration profile.
+In addition a separate NodeJS based frontend server will serve the javascript frontend resources and provide SSR with hydration.
+To deploy this setup using containers you will need the plone-frontend image of the frontend server. 
+
+This is the first release of Plone where the community has to work in and support 2 language and development stacks.
+The documentation has been rewritten, but for this first release you will find some repetition of concepts in the documentation structure. 
+For example for deployment or development setup.
+It will take some time before we will find the best structure to explain these new possibilities and expansion of Plone its capabilities.
 
 
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