Here is a PDF training material about the usage of EDI interfaces in Sales & Distribution module. The Electronic Data Interchange (EDI) component in Sales and Distribution consists of an Intermediate Document (IDoc) interface. You can use this interface for “send messages (outbound processing) such as an order confirmation through Electronic Data Interchange (EDI)” and “receive messages (inbound processing) such as a sales order through EDI”.
During outbound processing in Sales and Distribution, the system determines output using the output determination component. The system converts the data into an IDoc and issues it using the IDoc interface. During inbound processing, the sender converts the data into IDocs and passes it on to the IDoc interface. These IDocs are stored in the SAP System. In a second step, the system creates the document data.