Extend documentation with framework basics

README.md

@@ -1,6 +1,6 @@
 # baseimage-tutorial-framework
 
-This is the beating heart of TFW – the Docker baseimage consisting of the backend internals of the framework.
+This is the beating heart of TFW – the Docker baseimage containing the internals of the framework.
 
 All tutorial-framework challenges are child images of this one: their `Dockerfile`s all begin with `FROM avatao/tutorial-framework`.
 
@@ -9,4 +9,15 @@ This document explains the general concepts of TFW and should be the first thing
 For more on building and running you should consult the `test-tutorial-framework` repo.
 
 ## The framework
-*... in progress ...*
+
+The goal of the tutorial-framework is to help content developers in creating interactive tutorials for the Avatao platform.
+
+To make this possible TFW implements a robust messaging system and provides several pre-written components built upon it, such as a file editor or a terminal (running in your browser).
+
+The foundation of the whole framework is the messaging system connecting the frontend with the backend.
+Frontend components use websockets to connect to TFW, which you can hook to several *event handlers* to define ways to handle specific messages.
+
+![TFW architecture](docs/tfw_architecture.png)
+
+Note that our reference frontend implementation is written in Angular (`frontend-tutorial-framework` repository).
+Most of pre-made `EventHandler`s are writen in Python3, but you can write event handlers in any language that has ZeroMQ bindings (this virtually means any language).