Virtual Reality (VR) is a computer generated simulation of a 3d environment. Many times the user can interact with the content. In very simple forms, users view these environments through a headset that blocks out regular reality and replaces what a viewer sees with this simulated environment. In more complex virtual reality experiences, the user might wear gloves or hold objects that are used to interact with the simulation. Virtual reality can be used to experience places that you would not normally be able to.
Google Cardboard is a new way to experience virtual reality. What makes the Google Cardboard experience a little different than virtual reality devices in the past is that you truly have the option for 360 degree viewing. Google Cardboard is an inexpensive way to introduce K12 students to virtual reality. Following simple assembly, students can download educational apps and place their smart phones into the device within minutes. When setting up Google Cardboard, it's important to download the "Google Cardboard App" from either the Apple App Store or the Google Play Store (depending on OS).
For a general article on integrating VR for classroom uses, see https://www.edsurge.com/news/2015-10-18-five-easy-ways-to-teach-with-virtual-reality-now.
A little bit about VR (pdf - 128KB)
Virtual Reality and Augmented Reality Basics (pdf - 296KB)
Create your own VR and AR experiences (pdf - 284KB)
Special thanks to Graduate Assistant Ryan Loyst for finding these resources