How to Create an Entity Relationship Diagram

Entity-relationship diagrams are used to plan and design a database for normalization purposes.
The entity-relationship model starts with the entities, data normalization starts with the attributes, and the two tools tend to verify each other. The entity-relationship model’s entities, attributes, and relationships map smoothly to a physical database.
ERD gives a clear, high-level logical view of the data in a system. It is an excellent starting point for modeling the system.
Before creating an entity-relationship diagram, the analyst must have at least a preliminary sense of the system’s logical entities, attributes, and data structures. The necessary information is obtained during the information gathering and problem definition stage Entity-relationship diagrams are important tools in the structured requirements methodology and in database design.An entity is an object (a person, group, place, thing, or activity) about which data are stored. A relationship links two entities and is shown by drawing a line between them.
Logically, a relationship can be stated in the form of a sentence with a verb linking the two entities.  However, the entity being displayed as reference are only example of an entity name or a table in your database.  Remember that you still need to add data fields for your table.  Moreover, you have to connect some entities as necessary especially if there is a foreign key within your table.