A Venn diagram is a diagram that shows all possible logical relations between different sets. Venn diagrams are used in set theory and probability to illustrate logical relationships, especially equivalence relations and their logical consequences. A Venn diagram consists of a finite number of overlapping closed curves, usually circles, each representing a set. The sets are shown as regions within the diagram. The area of the region that lies outside all of the circles represents the intersection (or union) of all sets in the Venn diagram.