An entity is an object in the real world with an independent existence and can be differentiated from other objects
An entity might be
- An object with physical existence. E.g. a lecturer, a student, a car
- An object with conceptual existence. E.g. a course, a job, a position
An Entity Type defines a collection of similar entities.
An Entity Set is a collection of entities of an entity type at a point of time. In ER diagrams, an entity type is represented by a name in a box.