The RequiredProdInfo component, which appears in the Product Info stage of an order processing pipeline, iterates through the OrderForm’s items list, and deletes any items that have the delete field set to 1 (presumably by a previous Product Information stage component, such as QueryProdInfo or QueryProdInfoADO).
If the RequiredProdInfo component deletes any items from the items collection, it retrieves the value of the pur_badsku message from the MessageManager, and writes this value to the OrderForm's _Basket_Errors collection.
If you are not running the Pipeline Editor in expert mode, the RequiredProdInfo component is automatically inserted into the Product Information stage, and is not visible through the Pipeline Editor user interface.