A Hasse diagram is a graphical representation of a partially ordered set (poset). It visually illustrates the relationships between elements, showing how they are ordered without explicitly displaying all the connections. In a Hasse diagram, elements are represented as points, and lines connect them to indicate the order, with higher elements placed above lower ones. These diagrams are useful in various fields, including mathematics and computer science, for understanding hierarchical structures. They help in visualizing concepts like lattices, set theory, and relations, making it easier to analyze the properties of ordered sets and their elements.