A Venn diagram is a diagram that shows all possible logical relations between a finite number of sets. A Venn diagram is usually drawn as an overlapping circle, with each set as a different-sized circle inside the larger one. When two circles don't overlap, they represent sets that have no elements in common. When two circles overlap completely, they represent sets that have every element in common. This type of Venn diagram is called a 2 triangle because there are two overlapping circles in the shape of a triangle.