Wiktionary
alt. (context usually attributive computing English) A feature of a graphical user interface whereby the user can drag a visual item across the screen and drop it in another location. n. (context usually attributive computing English) A feature of a graphical user interface whereby the user can drag a visual item across the screen and drop it in another location.
Wikipedia
In computer graphical user interfaces, drag and drop is a pointing device gesture in which the user selects a virtual object by "grabbing" it and dragging it to a different location or onto another virtual object. In general, it can be used to invoke many kinds of actions, or create various types of associations between two abstract objects.
As a feature, drag-and-drop support is not found in all software, though it is sometimes a fast and easy-to-learn technique. However, it is not always clear to users that an item can be dragged and dropped, or what is the command performed by the drag and drop, which can decrease usability.