It is not easy to simplify what culture means. It can be defined in different aspects. The sociological meaning of culture is "a manifestation of the way people act, talk, dress, eat, drink, behave socially, and practice their religious beliefs. Culture also spans ethnicity, economic situation, place of work, gender, age sexual orientation, physical handicap, geographic location, and many other aspects of a person's life" (Lester, 1995, p. 71). Peterson (1979) states that when sociologists talk about culture, they usually mean one of the four things: norms, values, beliefs or expressive symbols.
The cultural studies definition of 'culture' is "the practices and processes of making meanings with and from the 'texts' we encounter in our everyday life... cultures are made from the production, circulation and consumption of meanings. To share a culture is to therefore, to interpret the world - make it meaningful - in recognizably similar ways" (Storey, 2003, p. 3).
According to Sturken and Cartwright (2009), visual culture is where the "shared practices of a group, community, or society in which meanings are made out of the visual, aural and textual world of representations and the ways that looking practices are engaged in symbolic and communicative activities".
I will take the Harry Potter movies as an example to show my understanding of this theory.
To understand this theory, main terms such as representation, discourse, ideologies and politics should be kept in mind.

Now, the Harry Potter films represent the magical world of witchcraft and wizardry where these stories tell the adventures that an orphan and his friends had to go through throughout their 6 years of magical education in Hogwarts. On the other hand, discourse means cultural framework. With discourse comes ideologies. What are the ideologies of the Harry Potter films? That would be witches and wizards, wands and broom sticks, fighting trolls and other mystical creatures. However, one must bear in mind that ideologies in a discourse may not be entirely true. Then comes politics and it simply means struggle over meaning. Politics can be found in Media and the Harry Potter films are included too. For example, politics of femininity and masculinity, politics of individuality and agency, politics of gender relations, politics of class, etc.
I can find 'culture' everywhere. I see and I hear it everywhere. In studying Communication, one must be analytical of what is going on around oneself. This theory makes me notice how much the simplest things like the Harry Potter films or even Facebook could be a 'culture'. We can be oblivious of how these things come with ideologies and it is those values that must be represented in order for people to understand.
References:
Griffin, E. (2012). A first look at communication theory. New York: McGraw-Hill
Storey, J. (2003). Cultural Studies and the Study of Popular Culture. United States: University of Georgia Press
Sturken., M., & Cartwright., L. (2001). Practices of Looking: An Introduction to Visual Culture. United States: Oxford University Press