The Snapchat feature allowed users to see their friends' location on a map - which, as many people pointed out, is a pretty large invasion of privacy.
Facebook now has a similar feature, but instead of mapping locations with map-like accuracy it will tell you when friends are in the nearby area.
It's only accessible through the mobile app and displays the neighbourhood your Facebook friends are in when nearby.
The feature is called "Nearby Friends" and we're not entirely sure of its purpose. Surely if you want to let someone know you're in the area you'll just text them right? Or Facebook message them if you want to stay attached to the app in some respect.
Here's how to turn it off:
Menu button > Explore > Nearby Friends (it may already be disabled, in which case no changes are necessary).
From here go to gear button/settings and swipe the 'Nearby Friends' button at the top to disable the function, or customise it for certain friends groups.