A Venn diagram is useful for highlighting overlapping concepts or objects. The overlap, known to some as the hedgehog or the nut, represents how these things relate. In this example, both pizza and movie relate to Friday night at home.
This same technique can be used to sort things into sets based on how they're similar. For example, we might make a circle for movies we love and one for movies referencing pizza, and put the movies we love that reference pizza in the overlap.