Can someone pls explain

Question

I don't really understand their explanation

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
: https://www.html5rocks.com/en/tutorials/dnd/basics/

Answer 2

thanks a lot for the link
any other explanation. ...........anyone??