Parent Billing allows you to create categories within your product catalog. Adding a category to an item groups similar items in the same category together - making it simple to view consolidated sales reports by category.
To create or add a category to an item, simply edit an item from the detail page, and enter in a title under category. Select save - and going forward this will create an existing category for you to choose from.
If you have previously created a category, you can select from an existing category for all new and existing items you create. You also have the option to edit the category of a catalog item - which will recategorize the sales of those items under its new category going forward.