how to use the Drag-Drop API?

Answer 1

Drag and Drop is a part of HTML5, you can see how it works at w3 School: http://www.w3schools.com/html/html5_draganddrop.asp in this site you can study the code and try it out as well. For a bit more detailed information: https://www.html5rocks.com/en/tutorials/dnd/basics/

Answer 2

you can use HTML 5 API, but you need understand basic JavaScript before use this.