I believe individual shippers prepare Bills of Lading, which are legal contracts for the carriage of the goods and a description of them, on the railroad's form. The Waybill is a document generated by the railroad covering the details of the shipment, including the route, the destination, the train and car number, the consignee, the charges and prepayments, and so on, and comes after the Bill of Lading.
The Union Pacific's Web site has a glossary for its customers that defines a lot of these terms and gives explanations here http://www.uprr.com/customers/ncsc/glossary/index.shtml The rest of this site is useful for the information the UP, and presumably other railroads, provides from its customers and expects from them.
