Classes are used to departmentalize financial transactions in the QuickBooks general ledger and All Orders inventory ledger.    

To create an Account Lists --> Profile Lists --> Class and click Save & New.   Enter a short Name and Sub Class (if applicable) then click Save, Save & Close or Save & New.

Note, if you are connected to QuickBooks you cannot edit classes through All Orders.  You must edit the account in QuickBooks then synchronize.