The NONCATEGORY ITEM NAME field is the name of the item that will be used on the invoice for your any sales that are not in a category on your point of sale system. This will only be used if you turn on the BY CATEGORY option. If you have the BY CATEGORY option turned off, then the invoice will use one item for the combined sales of all your categories. A sample invoice is shown below with the default NONCATEGORY ITEM NAME highlighted in red.
If you do not have an existing item in your accounting system that has this name, then a new one will be created. The default account name for this new item is "Sales of Product Income" and the sub type is "SalesOfProductIncome".