How '5-D' glass discs can store data for billions of years

Researchers at the University of Southampton say they have created a way to store information for billions of years. How does the new format work, and why is it important to store data for the long haul?
http://m.csmonitor.com/Technology/2016/0217/How-5-D-glass-discs-can-store-data-for-billions-of-years