VCL :: 
Moving an object with the mouse button pressed is usually called dragging, and what happens when we end dragging by releasing the mouse button is called dropping.
Moving an object with the mouse button pressed is usually called dragging, and what happens when we end dragging by releasing the mouse button is called dropping.
Delphi makes it easy to program dragging & dropping into our applications. We can even drag and drop from one form to another or from Windows Explorer to our application, or from-to what ever we want, as you will see.
Read the full article to learn aboutDrag and Drop Operations In Delphi
Related:
Drag-n-drop is always a good operation to support in an application.