What is Meaning of upstream and downstream partners?

Supply chains are the suppliers, manufacturers, distributors and transportation modes that move products and services from the source of components and raw materials to the customer. Product flowing from the source toward the customer is flowing downstream. Activities that are performed previous to a specific point on the supply chain are upstream activities. (source: http://www.ehow.com/info_8745500_upstream-downstream-supply-chain-activity.html)