Li are the rules of etiquette which regulate Chinese life. The original meaning was ‘to sacrifice’ and came from the Confucian tradition of proper behaviour promoting a harmonious atmosphere. The rules, in a slightly modified form, are still part of Chinese society today.
Learning ‘li’ was important as it covered how people inter-reacted with those of other ages and classes. There were four basic tenets to li, being moderation (staying between extremes to keep harmony and balance), fulfilling your allotted role in life (for example if you are a father, then you should be or act as a father), keeping relationships within the family correct and revering the aged and ancestors. However there were hundreds of rules stemming from these four ideas and people were often judged on their standard of education by how well they followed them. The higher the class you belonged to, the more demanding the rules to be followed. Harsh punishments were often imposed for breaking the rules.
Nowadays they are considerably more relaxed, but still expected, especially in formal and business situations.