Form parts are used for two purposes. One is to provide a popup form as you hover over a foreign key, such as the popup when you hover the Product number when entering sales or purchase orders. This is great for users, as it means they don't necessarily have to navigate away from the task they are performing.

Another use is to create a reused form part that we can place within other forms. We could have a form part that contains product information, which we could add to the product and sales order forms. We can specify a link when we add the form part, making them easy to implement.