An Entity-Relationship Diagram (ERD) is a type of flowchart that illustrates how entities, such as people, objects, or concepts, relate to each other within a system. ERDs are most often used to design or debug relational databases in the fields of software engineering, business information systems, education, and research. ERDs are composed of entities, relationships, and attributes, and they depict cardinality, which defines relationships in terms of numbers. Here are some key features of an ERD:

• Entities: A definable thing, such as a person, object, concept, or event, that can have data stored about it. Entities are typically shown as rectangles.

• Attributes: Characteristics of an entity that describe it. Attributes are typically shown as diamonds.

• Relationships: Connections between entities that describe how they are related. Relationships are typically shown as lines or other symbols.

ERDs are usually drawn in a graphical form as boxes (entities) that are connected by lines (relationships) which express the associations and dependencies between entities. ERDs are used to model and design relational databases in terms of logic and business rules (in a logical data model) and in terms of the specific technology to be implemented (in a physical data model). ERDs provide a visual starting point for database design that can also be used to help determine information system requirements throughout an organization.