The subform with order details is nested in the subform of orders, which is embedded in the main form of customer records.
In the same way that it can be convenient to have a subform inside a main form, it can be equally convenient to have a subform inside another subform. A subform inside a subform is called a nested subform.
For example, consider a Customers main form that displays the details of all your customers. An embedded Orders subform displays orders placed by each customer, and a nested Order Details subform displays the details of each order. The form and the subforms are connected to tables in one-to-many relationships. One customer can have many orders, and one order can have many details.
How many subforms can you put inside other subforms? You can nest as many as seven levels. If you don't need nested subforms, however, there's no limit: You can embed as many subforms as you like in any main form.
How do you create nested subforms? You'll see later on.