Friends

If any of your friends have also found the cache, a Friends icon will appear along with the usual Map, Open and Notes. The Friends action will show you a list of all of your friends who have logged it and if yoiu tap their name, will open geocaching.com to their log.

Make sure you and your friends have enabled the "Allow Authorized Developer applications to share..." function on geocaching.com https://www.geocaching.com/account/settings/authorizations