Android Nougat’s “Seamless Updates”, Explained
 

In all generations of Android devices—up to an including Marshmallow—operating system updates have essentially worked the same way: the update is downloaded, the phone reboots, and the update is applied. During this time, the phone is rendered useless, at least until the update has been fully installed. With Nougat’s new “Seamless Updates,” this model is a thing of the past.

http://www.howtogeek.com/269595/andr...tes-explained/