They are referring to two different networks. The U.S. has lots of different 'terms' defining how sensitive information is. Secret, Top Secret, Classified, Protected, etc. etc. They have both protected, unclassified networks, and secure classified networks.
Although I've only seen the truly secure pentagon stuff (in pictures and stuff) via ethernet. Check out any pictures of the "situation room" or other high profile, highly classified areas within the pentagon. All of the laptops are connected via ethernet (tagged with 'classified' ribbons around the cable).
My younger brother is in the Navy and works in information security and network administration. He says they use ethernet alone for everything classified. So one might think that the 'protected unclassified' would be a form of secure Wi-Fi for devices. Or just a separate network entirely. I wouldn't be surprised if the 'secured classified' network was completely isolated, not physically or otherwise connected to any other network OR to the internet.
Interestingly though, this article makes it seem like the iPhones and Android devices would be connected to what they are describing as 'secured classified'. So maybe they are opening up the classified (or already have) network to Wi-Fi?
Who knows. Sure is pretty interesting though.
