API stands for application programming interface. When building computer applications, an API allows a software developer to perform basic functions and define the proper way for programs to interact.
For example, if one software program needs to ask another software program to do something for it, the API is the mediator or broker between the two programs. The asking program uses standardized APIs that have been developed and defined specifically for the program upon which it is calling. Simply put, an API allows the programmer to get a job done without having to worry about how the underlying technology works.