Previously unique to Project Fi cell service, Google‘s Wi-Fi Assistant is coming to Nexus users as a way to save on data.
What it basically does is to connect your device automatically to other open and free Wi-Fi hotspots so you can save on data. As of now, it is available to Nexus phone owners in the US, Canada, Mexico, United Kingdom, and some Nordic countries. Unfortunately, it’s still not available here in the Philippines and they haven’t disclosed if it will be available to more regions.
In case you’re in one of the aforementioned countries, you can find Wi-Fi Assistant by going to: Android Settings>Google>Networking, then toggle the switch for the feature on or off.
{Source}