So what's API

If you have written programs for the Windows platform using Visual Basic (or Delphi or VC++ for that matter) then you have used the Win32 API, at least indirectly. Because, quite simply, any program you write for windows in VB, uses the Windows API. Each and every line of code you write is translated into corresponding API calls which the system uses to get the tasks done.

API (Application Programmers Interface) is a set of predefined Windows functions used to control the appearance and behaviour of every Windows element (from the outlook of the desktop window to the allocation of memory for a new process). Between them, these functions encapsulate the entire functionality of the Windows environment. So we can consider API as the native code of Windows. The other languages act as an attractive and often user-friendlier shell to the API promoting easier and automated access to it. An example is VB, which has replaced a sizeable portion of the API with its own functions. But every line of code written in VB is converted to its equivalent API calls.