In the world of Android software updates, Nexus devices tend to see the most of what Google has to offer and this is no surprise considering they're the poster children for what Google's vision of Android is. The latest version of Android is still Android 5.1.1 Lollipop, but sometimes we see multiple builds of a single version, and in this case the latest build for 5.1.1 has just been posted up to the Android Open Source Project, also known as AOSP. For the most part, the files and data in AOSP will only be usable or matter for developers as they're likely the only ones who will be needing to work with it. For the average user however, once a factory image has been uploaded then it becomes useful to non-developers.
As one would have it, Google has posted up the factory image for this latest build of Android 5.1.1, labeled as build LMY48G, for the 2013 WiFi only Nexus 7 tablet. This latest build of for the Nexus 7 on Android 5.1.1 Lollipop isn't going to have too many changes that will be noticeable on the front end, but that doesn't mean you shouldn't be a little excited. Chances are this is an update that holds some fixes for a few bugs that are present, and any fix for a bug is a good thing even if there is nothing new besides those fixes for the software.
This may be a new software build for Android 5.1.1 specifically for the Nexus 7 since there have been more than a few people who have had their tablets rendered inoperable due to Lollipop updates. Perhaps this is an update to fix those issues and perhaps it's not. It's quite likely though that is directed only at bug fixes since this isn't a new software version entirely, rather just a new build version. If you aren't one to wait on software OTA's to roll out, you can grab the factory image from the link above and flash it yourself but we only recommend doing so if you know your way around that process, otherwise it's best to just leave things be and wait for the build to hit your tablet normally.