A new month means a new security patch for Nexus device owners, and just a few days into the month Google has not only released the April 2016 security patch bulletin but they have also now published the factory images for the supported Nexus devices. Google states that they have begun the process of pushing out these over-the-air updates to the devices which are still supported, so between now and the next week or so those who are using a supported Nexus device should start to receive the software updates to their phone or tablet, although it might be soon for some users but later for others.
If you're the type of person who doesn't like to wait around and you are aware of the process for flashing new software manually and on your own, the factory images will allow you to update your device to the latest version of software that has the included security fixes for the patch this month. Supported devices include the Nexus 6P and the Nexus 5X with available builds for Android 6.0.1 MHC19Q, the Nexus 6, the Nexus 9 LTE model, the Nexus 7 (2013) mobile model, and the Nexus 5 have available builds for Android 6.0.1 MMB29X, and the Nexus 9 WiFi, the Nexus 7 WiFi, and the Nexus Player all have builds available for Android 6.0.1 MOB30D.
As these are factory images of the software, there will be no difference in the software that you flash from the software that Google would push out to your device, however, it's worth considering that it might be better to wait for the OTA download to be pushed out to devices if you have never flashed Android software to a device before. Having said that, it can be a straightforward process if you read through instructions on how to flash the factory images and you have the needed tools to get the software onto your device. It shouldn't be too long before most users start to receive the updates over-the-air, so if you're uncomfortable with flashing the factory images for fear of damaging your phone or tablet, the security patch will be pushed out soon enough.