From LXF Wiki
API is an acronym for Application Programming Interface.
An API is best described as a collection of pre-defined routines that a programmer can call upon, along with a model of how the routines work together, to produce working software. APIs are usually associated with programming languages, where the programmer 'sees' only the application layer and is therefore shielded from having to cope with the specific hardware or software idiosyncrasies of the resident computer or Operating System. Most modern languages have APIs written for them, the most common being [Java (http://www.activrobots.com/)], but some older languages suchas C++ also have APIs where the code/routines have been tailored specifically to a given area of work, such an example that the author has used, is a C++ API called ARIA which was designed specifically for use with Actimedia Robotics.