Assuming, you are asking for HTML Drag and Drop, it works fully on the Document Object Model(DOM). HTML drag and drop uses the DOM event model and drag events(like mouse event etc). On the event completion, the element's DOM changes to get to the dropped location. So short answer would be, "DOM manipulation by DOM event model".
May be I didn't understand the question fully. Let me know if this answers.
P.S: I think, you got to change the title. However the current title Dragged me to this question 😊.