Every production order will have at least one raw material (or component) in its Bill of Materials. It will also produce at least one product. The result is that your inventory is changed.
A production order does not automatically change the inventory levels. You have to create one or more production input documents on the production order manually to remove inventory from a location and add it to the Work in Progress production process. Once finished goods are ready, you have to manually create one or more production output documents on the production order to add the finished items to a location from the Work in Progress process.
Production Input and Output documents can be viewed on the Inventory screen under the "Internal" tab.
A production output document is also used to assign serial numbers, batch numbers and expiry dates to items produced in your production process.