What are entities

In the context of data modeling and databases, entities are fundamental components that represent real-world objects, concepts, or things that have distinct existence and are of interest to an organization or system. Key points about entities include:

1. **Definition:** Entities are objects or concepts about which data is collected and stored. They can be physical objects (e.g., employees, products) or abstract concepts (e.g., transactions, events).

2. **Attributes:** Each entity has attributes, which are characteristics or properties that provide more details about the entity. For example, an "Employee" entity might have attributes such as Employee ID, Name, and Department.

3. **Instances:** Each entity can have multiple instances or records. For example, the "Employee" entity might include individual records for each employee in the organization.

4. **Entity Types:** Entities are categorized into entity types based on their roles and characteristics. For example, in a database for a retail store, there might be entity types such as "Customer," "Order," and "Product."

5. **Relationships:** Entities are often related to other entities through relationships. For example, an "Order" entity might be related to a "Customer" entity through a "placed by" relationship.

In database design, entities are represented in Entity-Relationship Diagrams (ERDs) as rectangles, with relationships and attributes clearly depicted to illustrate how data is organized and interrelated.