describe the use-cases of the tutorial

Author: niccokunzmann

README.md

@@ -1,15 +1,30 @@
-# intro
+Programming Introduction Tutorials
+==================================
 
 [![Join the chat at https://gitter.im/CoderDojoPotsdam/intro](https://badges.gitter.im/CoderDojoPotsdam/intro.svg)][gitter]
-[![PRs Welcome](https://img.shields.io/badge/PRs-welcome-brightgreen.svg)](http://makeapullrequest.com) 
+[![PRs Welcome](https://img.shields.io/badge/PRs-welcome-brightgreen.svg)](http://makeapullrequest.com)
 [![Build Status](https://travis-ci.org/CoderDojoPotsdam/intro.svg?branch=master)](https://travis-ci.org/CoderDojoPotsdam/intro)
 [![Docker Build Status](https://img.shields.io/docker/build/coderdojopotsdam/intro.svg)][dockerhub]
 [![Offline Servers Online](https://intro.quelltext.eu/announce.svg)][server-branch]
 
 This is an introduction site for programming tutorials.
-You can view the website [here](https://CoderDojoPotsdam.github.io/intro).
+The following use-cases are considered:
 
-It is used by the following CoderDojos:
+1. [**View the website online**][page]  
+   The webpage is served by GitHub pages.
+   You can view it online any time you want. Even after a meeting,
+   you can continue to use it at home.
+2. [**Download the website for offline usage**][offline-download]  
+   You can distribute it with a USB-Device.
+   Some of the tutorials are available offline and vilibly marked.
+3. **Distribute the webpage locally**  
+   You may install the [offline server][server-branch] on a local computer.
+   People can access it without an internet connection.
+   With a low-bandwidth internet connection, they can choose a local
+   server from the menu and work on local tutorials.
+   This frees up the internet connection and speeds up response time.
+
+This page is used by the following CoderDojos:
 
 - [CoderDojo Potsdam](potsdam.html)
 - [CoderDojo Dahlem](dahlem.html)
@@ -21,3 +36,5 @@ If you have any questions or like to get in touch, [join our chat on gitter][git
 [gitter]: https://gitter.im/CoderDojoPotsdam/intro?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge
 [dockerhub]: https://hub.docker.com/r/coderdojopotsdam/intro/
 [server-branch]: https://github.com/CoderDojoPotsdam/intro/tree/server#readme
+[page]: https://CoderDojoPotsdam.github.io/intro
+[offline-download]: https://github.com/CoderDojoPotsdam/intro/archive/offline-build.zip