ERD

ERD is Entity Relationship Diagram, and it is used to document all tables and fields required in the database that stores the data in your project.  For example, when someone logs into your site, their username and password need to be looked up.  That information is located in a data storage program called a Database.  Each Database stores its data in Tables.  A Table resembles an Excel worksheet, with rows and columns.  In Database terms, a row is called a "record," and a column is called a "field."  So, the ERD documents each and every field and table, and shows how they are related to organize and store all data for your project.

The sample ERD below shows the storage and organization of Customer Data, which includes the customer data, the addresses associated with each customer, the contacts for each customer, the invoices and phone calls for each customer.