Answer:
Norms are the social rules that govern behavior in a community. Norms can be explicit (such as laws) or implicit (such as codes of polite behavior). Norms can be difficult to identify because they are so deeply instilled in members of a given society. Norms are learned by growing up in a particular culture and can be difficult to learn if one does not grow up in the same social milieu.
The act of violating a social norm is called deviance. Individuals usually have a much easier time identifying the transgression of norms than the norms themselves. For example, few Americans would think to tell a sociologist that it is a social norm to hold the door open for a fellow pedestrian entering a building if within a particular distance. However, someone might remark that another person is rude because he or she did not hold the door open. Studying norms and studying deviance are inseparable endeavors.