ERD is a model which is used to show the relationship between entity and data base. I created this basic diagram to represent the online recipe website. So each boxes are connected to each other in a one way. As an example, For online recipe websites, User is the first step which can upload recipe. Each recipe can uploads comments and images.
This diagram has only four categories, User, Recipe, Image and comment. To create ERD it has to be 4 categories at least but it can be more than 10000. It depends on a websites.
The arrows between each section shows the relationship between the categories which means there is an order for each.
Each categories has Foreign key and Primary key.Each categories has primary key to connect with another category as a foreign key.