Every culture has formal norms and informal norms. Formal norms are usually written down as laws and regulations. They're enforced by the community, like a traffic ticket. Informal norms can be more difficult to determine, since they aren't written down. Things like holding the door for a stranger are not written into law. You can learn the informal norms of a culture by talking to, reading about, and observing the normal behaviors of people living in that culture. To effectively operate in any culture, you've got to know the formal norms and the informal norms. Culture matters.