There is no article description for item 000001

Working with Genrtan server for Windows and ECC 6.0 we are receiving an error when we import IDOC. The IDOC is an 850 PO from a customer. The document imports correctly except for it is a status 51 with the text message as "There is no article description for item 000001 “. I have searched and cannot find any documents that explain what the error refers to. What is an ARTICLE with reference to SAP? How can i resolve this error?