This is Google Cardboard. It's really, really weird.
Here's the gist: Google is experimenting with virtual reality displays at I/O 2014, including a new VR toolkit for developers to try out. They've also created an Android app that will let you simulate an Oculus Rift-style, dual-screen VR headset using only your phone, kind of like that Samsung rumor from last month. Here's the problem: you don't have a headset. Google I/O attendees are getting free headsets that they can build out of cardboard, which then holds their phone at optimal VR-viewing distance.