More doc, link YouTube video.

README.md

@@ -1,6 +1,12 @@
 # MTSatellite
 
-MTSatellite is "realtime" web mapping system for [Minetest](http://minetest.net) worlds.
+MTSatellite is "realtime" web mapping system for [Minetest](http://minetest.net) worlds.  
+With this system you can play your world and you instantly have an online map of it which
+can be share on the web.
+
+To get a glimpse what it does watch [Realtime Webmapping for Minetest worlds](http://youtu.be/iYEROGPj7RI)
+on YouTube.
+
 To use it you have to configure your Minetest server to use the Redis backend data store.
 Instead of a real Redis server you have to run **mtredisalize**. This server stores the data
 in an optimized form and collects changes made to the world over a configurable amount