Business Application Programming Interfaces (BAPI) provide a way for third-party applications to synchronously integrate with SAP at the object level. You can use BAPIs to read, create, change, or delete data in SAP.
SAP provides the ability to remotely call business functions through Remote Function Call (RFC). BAPIs are a subset of the RFC-enabled functions published by SAP in the Business Object Repository. BAPIs are published as methods of SAP business object types that perform specific business functions. BAPIs allow access to the SAP system objects through methods for the business object types. Together with the business object types, BAPIs define and document the interface standard at the business level.
The SAP BAPI Connector is available as a service call in Application Integration. For example, to update the sales order data in SAP, you can configure an SAP BAPI connection to access the BAPI_SALESORDER_CHANGE function.
You can view and test the BAPI interface definitions in SAP using transaction SE37.