what is er diagram in dbms

An Entity Relationship Diagram (ER Diagram) is a diagram that represents relationships among entities in a database. It is a structural design of the database created with specialized symbols for defining the relationship between the database entities. ER diagrams are used to model real-world objects like a person, a car, or a company and the relation between these real-world objects. ER diagrams are widely used to describe the conceptual design of databases and help both users and database developers preview the structure of the database before implementing it. ER diagrams are based on three principal components: entities, attributes, and relationships. Entities may be any object, class, person, or place, and are represented as rectangles in the ER diagram. Attributes are represented as ellipses, and relationships among entities are represented as diamonds. Lines represent attributes to entities and entity sets with other relationship types. ER diagrams are easy to understand and create, even for a naive user, and require no technical knowledge or hardware support.