EDI means Electronic Data Interchange and is used between SAP systems and external systems. When thinking about MM-IV processes, EDI enables a vendor to transfer invoice information electronically instead of in the form of a printed paper invoice. IDOC means Intermediate Document, and is used during ALE and EDI processes. An IDoc is generated for each invoice and the system posts an invoice using the data in this IDoc. ALE is a component in SAP and means Application Link Enabling. It is used between SAP systems. ALE is generally used to transmit Master Data information as material, vendor, customer, conditions, etc.