SAP R/3 is the former name of the enterprise resource planning software produced by the German corporation SAP AG (now SAP SE). It is an enterprise-wide information system designed to coordinate all the resources, information, and activities needed to complete business processes such as order fulfillment, billing, human resource management, and production planning.
Remote Function Call is the proprietary SAP SE interface. Remote Function Call (RFC) is the standard SAP interface for communication between SAP systems. The RFC calls a function to be executed in a remote system. Remote function calls may be associated with SAP software and ABAP programming and provide a way for an external program to use data returned from the server.
ABAP (Advanced Business Application Programming) is a high-level programming language created by the German software company SAP SE. It is currently positioned, alongside Java, as the language for programming the SAP Application Server,