When considering concepts like culture or reality, it's important to remember that there is no universality. That means that there is no single culture or single reality; rather, each society and group has its own system of values, traditions, and beliefs that shapes their view of the world.
In the United States, for example, there is an American culture, but underneath that there are many sub-cultures and groups whose beliefs and experiences of reality are different. This is critically important because it shapes the ways in which groups and individuals understand or engage with one another.
Imagine that you're a young white women who was raised in a wealthy New England suburb populated by mostly white people. In your culture, there is very little poverty or crime and the activities in which you participate are generally geared towards people like you. In this case, your culture is shaping your reality: people live relatively safe stable lives and their financial stability provides them with many luxuries.
In this case, your reality is no better or worse than anyone else's, but it can make things challenging when you encounter people from other cultures that are more racially or ethnically diverse or from different social classes. For these people, their culture has shaped a very different reality in which there might not be financial stability or safety, which can create a very different value or belief system.
In simple terms, your experiences with your culture have shaped your reality, which can be very different from the culture and reality of others. When these two (or more) groups come into contact with each other, there can be misunderstanding, arguments over whose culture is more valuable or "right," and many other challenges that accompany a clash in perspectives.