Transfer transfers data from processed invoices to your target system, which utilizes that data or gives you access to it. The target system can be another application in the same computer as INVOICES or in another computer.
Target systems that handle the output data need that data to have a predictable structure. For example, in most output files, each record begins on a new line. The target system expects this. You use transaction descriptions to specify output that matches your target system's requirements.