Culture is the characteristics and knowledge of a particular group of people, defined by everything from language, religion, cuisine, social habits, music and arts.
The Center for Advance Research on Language Acquisition goes a step further, defining culture as shared patterns of behaviors and interactions, cognitive constructs and understanding that are learned by socialization. Thus, it can be seen as the growth of a group identity fostered by social patterns unique to the group.
Many countries are largely populated by immigrants, and the culture is influenced by the many groups of people that now make up the country. This is also a part of growth. As the countries grow, so does its cultural diversity.