A Hasse diagram is a graphical representation of a partially ordered set, illustrating the relationships between its elements. In these diagrams, elements are represented as points, and lines connect points to show the order relation. The diagram is drawn in such a way that if one element is less than another, it appears lower in the diagram. Hasse diagrams help visualize concepts in set theory and lattice theory, making it easier to understand the structure of ordered sets. They are particularly useful in mathematics and computer science for analyzing relationships and hierarchies among different elements.