IDOC is simply a data container used to exchange information between any two processes that can understand the syntax and semantics of the data.
In simple words , an idoc is like a data file with a specified format which is exchanged between 2 systems which know how to interpret that data.
IDOC stands for " Intermediate Document"
When we execute an outbound ALE or EDI Process, an IDOC is created.In an inbound ALE or EDI process, an IDOC serves as input to create an application document.In the SAP System, IDOCs are stored in database.Every IDOC has an unique number(within a client).
IDOCs are based on EDI standards, ANSI ASC X12 and EDIFACT. In case of any conflict in data size, it adopts one with greater length. IDOCs are independent of the direction of data exchange e.g. ORDERS01 : Purchasing module : Inbound and Outbound.IDOCs can be viewed in a text editor. Data is stored in character format instead of binary format.IDOCs are independent of the sending and receiving systems.(SAP-to-SAP as well as Non-SAP)