A Venn diagram is a visual tool used to show the relationships between different sets of items. It typically consists of overlapping circles, where each circle represents a set. The areas where the circles overlap indicate common elements shared between the sets, while the non-overlapping areas show unique elements. Venn diagrams are commonly used in various fields, including mathematics, logic, and statistics, to illustrate concepts such as intersections, unions, and differences. They help simplify complex information, making it easier to compare and contrast different groups, such as animals, mammals, and birds.