It shows two Venn diagrams (Harris loves Venn diagrams ... pussy-grabbing con-man like you can understand. The top diagram ...

Draw a Venn diagram ... The diagram shows us clearly who plays which sports, and also includes the pupils who do not play any sports, by placing their names outside of the circles.

Some venn diagrams have 2 circles inside a rectangle and are very simple. Here is a venn diagram with 3 intersecting circles.