The Product Categories module allows Users to structure Products into a hierarchical category structure. To create a Product Category record, navigate to the Product Categories module and click the ‘Create Product Categories’ button in the action bar.
The Parent Category field is a relationship field to another Product Categories record. If you check the ‘Is Parent Category’ field then this signifies that the category is the highest level. Once selected you will not be able to select a Parent Category using the relate field.