A new feature is built into Facebook's mobile app that allows you to see which of your friends are close by and even share your exact location with others. The new feature uses the geo location technology in your smart phone to determine when you are close to one of your Facebook friends. When activated, the feature will send periodic notifications to friends who are nearby. Users who did not activate Nearby Friends won't be affected in any way, and will not share with or receive any location information from others on the platform.
To know more about the use of this new feature visit the article by Kurt Wagner, Social media reporter for Mashable, http://mashable.com/2014/04/17/facebook-nearby-friends/