Application Programming Interface
This is the abbreviation for Application Programming Interface (API).
All software has to request other software to do some things for it. To achieve this, the asking program uses a set of standard requests called API. This is used for the program being called upon. Almost every application depends on the APIs of the underlying operating system to perform such basic functions as accessing the file system. In true sense a program's API defines the proper way for a developer to request services from that program. An API is said to grant access to or open an application.