A computerized system is like any system part of a greater whole, and communication with this "outside world" is supported by Idocs. Intermediate documents. A document which is in transfer (or it it in the process of being composed and sent out (outbound Idoc) or it is in the process of being interpreted (inbound Idoc). Idocs is SAP controlled manner of interfacing, and you should realize there is a strong preference over the "manual interface" as the system as a whole has little benefits from numerous stand-alone interface programs. Going from system to system the Outbound Idoc is first composed as a document on the tables of the sending system. It is then sent out as file or stream, to be picked up as an Inbound Idoc in the recieving system. The revieving system assigns a new Idoc number and stores the Idoc document. A stored document can then be processed, resulting in e.g. the creation of a Goods receipt or the change of an Order.
