Ever since KitKat, Android has verified your device’s boot process to make sure that rootkits and other forms of malware don’t operate undetected. However, it hasn’t done much more than alert you of potential problems (as of Marshmallow)… until now. Google explains that Android Nougat strictly enforces that boot check, giving you far more than just a warning. If your boot image or partition is corrupt, Android will either start in a limited-use mode (with your permission) or won’t start at all. The feature will first show up in devices that ship with Nougat out of the box.
Source: Android Developers Blog