You buy goods and dispose them in different storehouses and rooms. You can track quantity of the products in the each locations when you create receiving Item Receipts and Invoices.
When you move products from one locations to other you may use a transfer Order.
Select on the left menu Actions row "Transfer Orders" and click the button New. You should select source and destination location and enter the line items in the detail area, You can use Group for classification Transfer Orders.