What is "api"

API, of Application Programming Interface (or Application Programming Interface) is a set of routines and standards established by software for the use of its functionality by applications that do not intend to engage in details of software implementation, but only use its services.

In general, the API is composed of a series of functions accessible only by programming, and which allow the use of software features less evident to the traditional user.

For example, an operating system has a large number of functions in the API, which allow the programmer to create windows, access files, encrypt data, etc. But operating system Apis are often dissociated from more essential tasks, such as memory block manipulation and device access. These tasks are core system attributes and are rarely programmable.3 Another example is geometric drawing programs that have a specific API to automatically create entities according to user-defined patterns.

More recently, the use of API has become widespread in plugins (accessories that complement the functionality of a program). The authors of the main program provide a specific API for other authors to create plugins, extending the functionality of the program.

Source: Wikipedia (API)