Item charge it's used to when you purchase and item which purchase value it's for example 20 and you transport fee it's 10 when this item enters the inventory and every cost it's confirmed (invoiced) would have 30 (20+10). When you sell it (40) = you could have a profit of 10 (40-30) that would be more accurate than only the purchasing value.
Non inventory items are more focus on items that you don't want to keep track of their inventory. Test items from the vendor, office materials, ...
