This is a pre-release version of iOS 9.3 for iPhone, iPad, and iPod touch. Devices updated to iOS 9.3 can not be restored to earlier versions of iOS.
iOS 9.3 adds numerous new features to Apple's mobile operating system including: Night Shift, secure Notes, more personalized News, an improved Health app, updates to CarPlay, Verizon Wi-Fi Calling and new Education features. More details on those features here.
Developers can download the new build from the link below...