quantum satellite communication

ok so can someone ezplain this to me in a way i'll understand??

- http://www.smh.com.au/world/china-launches-hackproof-quantum-satellite-in-world-first-20160816-gqtk6g.html

I found this on youtube https://www.youtube.com/watch?v=ZuvK-od647c  but they are saying it only works 50% of the time.....eg totally random and not proven.

So is it actually a proven theory or "still testing" phase?

UPDATE: Just found this article, best explanation of the project I've read so far
- http://physicsworld.com/cws/article/news/2016/aug/16/china-launches-world-s-first-quantum-science-satellite