Friends is a complete and pure popular play and it is a sitcom about love, sex, careers and the time when impossible is nothing. Also the show is about the search for commitment and security and the fear of commitment and security. Most of all, it’s about friendship when you are young and single. In one city, your friends are your family.
2 Definition
2.1 Culture and American Culture 
    In China, the definition of culture in political books is: With respect to the political and economic terms, culture is all spirit activities of human and their products. Culture is a very broad concept, so it is difficult to give it a rigorous and precise definition. From a different perspective, it can define different concepts of culture, such as the definition of philosophy, sociology, anthropology, history, linguistics and so on. Therefore, there is no recognized uniform definition of culture. Generally speaking, culture is a social and history phenomenon, and it refers to the history, geography, customs, traditions, lifestyles, behaviors, ways of thinking and values of a nation or a country.
    The United States is a nation of immigrants, that is, different ethnics from all over the world intersect and collide here, forming a unique culture ---cultural melting pot. The core of American culture is inpidualism which emphasizes freedom of inpidual will and personal behavior, mainly in the fighting spirit and risk-taking behavior and the yearning for freedom.
2.2 Mainstream Culture and Marginal Culture
    Mainstream culture (also known as the official culture) is a culture advocated by the society of an era, and playing a major role in society, which has highly fusion power, the stronger force and wide spread power.
    In relation to the mainstream culture, the marginal culture is always vulnerable and secondary. It is produced in marginalized groups, who are often been overlooked or even discriminated. In the sense of dynamic development, marginal culture is a product of cultural interaction. As a result, marginal culture is many new cultures derived during the interaction of different cultures, in which some cultures learn from other cultural ingredients.  主流与边缘之间：论《老友记》中菲比的怪诞形象(2):http://www.youerw.com/yingyu/lunwen_22136.html