In today's world, many of us have a data limit with our wireless carrier. Whether it be a measly 1GB of something even higher. Many customers are having to watch their data usage so that they don't get hit with massive overage fees, or get hit with slower data - seeing as many US wireless carriers have opted to throttle your speeds once you hit your cap now. In Android 7.0 Nougat, there is a way to save data with the data saver. So you can have certain apps not run in the background when you are on a mobile data connection. However, Google has something that will work even better, without limiting your usage. It's WiFi Assistant.
WiFi Assistant was actually part of Project Fi, and what it does is pretty simple. It will automatically connect you to public hotspots so that you can still use your data, but it won't count against your data limit since it's not on your carrier's network. This isn't part of Android 7.0 Nougat, it appears to be one of those "exclusive" Nexus features, as Google notes in their Google+ post that it is currently rolling out to all Nexus users right now. Currently, it's rolling out in the United States, United Kingdom, Canada, Mexico and Nordic countries. Google also says that the feature will be rolling out over the coming weeks, so it's another staged rollout.
Like with Project Fi, when you are connected to a hotspot automatically by the WiFi Assistant, you will also be connected through the VPN that is built into Android. This is to keep you and your data safe when you are connected to unsecure hotspots like those found at Starbucks and other places. You will be able to see that you are connected to a hotspot thanks to the VPN logo appearing in the status bar, so you'll know exactly what's going on. It's a great feature that should help everyone save a bit of money on their smartphone bills each month, or at least save a bit of data - depending on your carrier, that data can rollover to the next month as well.