DragonDrop is intended to reintroduce some of the functionality lost with the death of tabbed windows. We all remember tabbed windows, who trod the Classic paths. We could drag an open window to the bottom of the screen, and a title-tab peeked up, readily displaying its contents at a click or a drag, and collapsing to insignificance at the slightest thought of dismissal.
Some used the tabs for quick-launching their favoritest of applications and documents, others for drop boxes or to get things out of the way.
They're back, sort of.