Fob on invoice in Quickbooks

FOB stands for free on board which means if FOB is marked while invoice is generated the transportation charge would not be there or you can say it would be free shipping for the goods which are calculated for the final order.
Invoice consists of FOB feature  which helps in knowing of the transportation or shipping charge in QuickBooks where an extra charge is applied where eligible for the the vendor or customer to different locations.
With FOB feature the responsibility of delivery of the product is vendors or sellers which means if the list of products are in FOB all the goods will be received to the customer and the responsibility will be of the seller. But if it is not the nominal shipping charges would be mentioned with the invoice to be paid by the customer.

Further Reading