BAPI is a new concept which enables interfacing of standalone applications with SAP. Beacuse of the flexibility provided by BAPI in SAP, third party applications and components can be interfaced and integrated in the business framework. If I have to define BAPI, I would put it as "BAPI is an interface providing access to a user to processes and data of business applications".

Thus, BAPI is nothing but an entry gate to the SAP R/3 system. In a organization, business partners, customers etc might need to access the R/3, to achieve this, BAPI can be used. In a business object repository BOR, a business object can be implemented as BAPI. One thing to keep in mind is that BAPI is assigned to one and only one object. I don't want to sound too technical, but some of the functions of a BAPI are -

- creating objects
- displaying and changing attribute of an object

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