Android M: Nexus 5 Doze battery test delivers amazing performance
Doze will activate when a phone or tablet is unplugged, stationary and has the screen off to conserve battery life. The feature basically forces apps to stay asleep, as Android M will prevent them from accessing the network and sync functionality, among other things. Apps can then resume normal activity when the device is awake again.
Source: Android M: Nexus 5 Doze battery test delivers amazing performance | BGR