NS5 will only be available online at the Google Play Store. It comes with a special version of Android KitKat that installs some new software, adds new features and restricts a few options. Chrome's data compression proxy is now used at the OS level, so all the traffic is routed through Google's servers and you can't disable this feature. Your phone is associated with a Google account, you can no longer disable location services or Google+ Auto Backup and there's a new sponsored card in Google Now that shows personalized recommendations. You'll also hear some relevant audio ads when calling companies or when you play your music.
It's a great opportunity for Google to test new software, find new ways to monetize its services and capture the value of free hardware. Building a platform that makes mobile phones accessible for everyone has always been at the heart of Android.
Update: This is a joke for April Fools' Day 2014.