The Entity-Relationship Model (ERM) visualizes the structure of data through entities (objects or things of significance) and the relationships between them. It is a foundational design tool in database management that helps define how data is stored, organized, and manipulated in a database system. In ERMs, entities may represent real-world objects (like users or products), and relationships describe how these entities interact with one another. Diagrams that represent ERMs typically include rectangles for entities, diamonds for relationships, and lines connecting them, illustrating cardinality and constraints.