zeb: but what does it do..?
Simply, the claim is that communications on it can not be hacked or intercepted. That's why there's been so much research effort focused on quantum computing and communications
Supposedly, all present communications can be overheard if you have the right gear. (Think the USA's Pine Gap facility near Alice Springs in the NT). Any telephone conversation in Asia (or Australia) can be overheard. Of course, if its encrypted you may not be able to decode it, but (again its a claim) with the advent of extremely powerful quantum computing, most current encryption could be decoded. So a different approach will be required to provide secure communications.
We're talking about some very complex stuff, and I admit I really don't understand it.
An overview of it has been discussed on a web-site specialising in this stuff, and it also reports (on Sept 30) :
"Earlier today, China's pioneering quantum satellite Micius facilitated the first-ever intercontinental video conference using a quantum communications network. The video call connected Chunli Bai, the president of the Chinese Academy of Sciences in Beijing, with Anton Zeilinger, president of the Austrian Academy of Sciences in Vienna, a distance of over 4,600 miles. It was the first real-world demonstration that showed that a global quantum internet is not only possible, but within reach. "