What term describes the act of showing how two things differ?

The term that describes the act of showing how two things differ is "contrast." When you contrast two items, you highlight the differences between them, focusing on what sets them apart in various ways, such as characteristics, qualities, or behaviors. This process is essential in analyzing and understanding subjects more deeply, as it allows one to identify unique attributes that may not be apparent when looking at each item in isolation.

In this context, comparison is often used to refer to examining both the similarities and differences between two subjects. However, since the question specifically asks about differences, "contrast" is the more precise term to express that particular action.