BAPIs (Business Application Programming Interface) are specific methods for SAP business objects, which are stored in the Business Object Repository (BOR) of the SAP system and are used for carrying out particular business tasks.

In the SAP system, BAPIs are stored as RFC-capable function modules in the ABAP Workbench Function Builder. BAPIs have standard business interfaces that enable external applications (with the help of SAP business objects) to access SAP processes, functions and data.

Client programs that use BAPIs to access SAP business objects can be part of the same SAP system, part of an external system (for example, a .Net application), part of an HTTP Gateway, or part of another SAP system.

If you want to use a BAPI to trigger a business process in another system, you usually use the synchronous communication method sRFC, because in most cases, you want the data to be returned to the sending system.

For asynchronous communication using BAPIs, ALE is used, with additional IDoc interfaces being generated for the BAPIs.