When activated, Find WiFi will show which locations near you offer free WiFi along with those locations' business hours, what kind of places they are and their network names. However, businesses have to opt in to this service by claiming their network on their Facebook Page. So, not every available hotspot is going to show up.
In the announcement, Facebook said it found the feature to be useful in areas where cellular data was lacking or for people who were traveling. And this is just the latest project meant to boost internet connectivity and, therefore, Facebook use. The company is also working on an undersea cable connection between Los Angeles and Hong Kong, internet-providing drones and laser-based internet access.
To get to the feature, click the "More" tab in the Facebook app and then "Find WiFi." The roll out begins today and is available for both iOS and Android.