Business Application Programming Interface (BAPI)
SAP BAPI (Business Application Programming Interface) is a standard interface to the business object models in SAP products. Programmatically, it is a method of an SAP Business Object Type or of an SAP Interface Type.
BAPIs are the primary method through which customer code and third-party applications interact with SAP products. BAPIs wrap the internal layers of SAP's business object model to ensure that all business logic, validations, and authorization checks are executed properly when accessing or changing business objects.