The badge description reads:
Shared a link to a question that was visited by [number] unique IP addresses.
What does this actually mean? How can one get these badges? If I send an email (or tweet etc.) to a friend with a link to a question, presumably the SE system wouldn't know about it. So does "share" here mean only within SE, e.g. if I post a link to a Puzzling question in the SciFi chatroom? Also does "visited" mean that all those people at different IP addresses have to reach the question via that link - and again how could the SE system know how they came to a given page?