Dubbed Nearby Friends, the new feature will allow you to see which friends are close by and share your precise location with them for a set amount of time. Additionally, you'll also get a notification when friends are in close proximity, so that you can meet up, or conversely, run for the hills in the opposite direction.
Now, I'm giving Facebook some undue grief here, because the one thing they make clear, whether through their official announcement or its accompanying help page, is that this is an optional feature, and one that is off by default.
To turn it on, head to your Facebook app and tap the three-bar "more" button, then tap "Nearby Friends". Once you click through the splash screens, you can select who you want your location information shared with and turn the feature on.
You can also enable alerts for this information by going to App Settings -> Notification Settings -> enable Nearby friends, although this is on by default when you turn on the service.
Have friends nearby? Share your exact location by tapping the compass button, then limit how long your location is available and add a note.
You can stop sharing your precise location, even before the time you set, by tapping the compass again.
You can also see your location history, which is a cool feature to check out where you've been. This information is only visible to you, and is tracked whether you're in the app or not. Hit the gear icon on the Nearby Friends page, tap on Location Settings, and toggle the service on.
To view information, head to your profile, tap on Activity Log, select Filter, then scroll down to Location History.
This information is also viewable, through the same process, on the Facebook website.
Facebook is really pushing the ease at which you can turn the feature off, and it is very easy to do. Just like above, hit the gear icon, and toggle the service off. While there, make sure to turn off Location History as well if you don't want to be tracked.