Hey there! Hello!
The answer to this problem is most likely group norms. The definition given above pretty much explains it: they're an unspoken/unwritten set of informal rules that dictate a group member's actions.
They allow for people to know how to act in social situations while also knowing who is acting out of place according to the group norms. It's a bit difficult to understand exactly what they are, since they are unstated and all.
Hope this helped you out! Feel free to ask me any additional questions if you have any.
–Lamb :-)
