AjaxDraggable represents one half of the drag-and-drop implementation in Ajax framework. AjaxDraggable uses a WOComponentContent, so any content that you would like to be draggable should appear inside of the AjaxDraggable's webobject tags.
One element of the AjaxDraggable/Droppable implementation that is particularly cool is that you can actually bind a full-blown object to your Draggable that will be delivered to your Droppable when the drop action is fired. You never have to deal with maps of IDs and manual lookups. The Ajax framework automatically handles that for you.
An example of the Scriptaculous drag-and-drop is available here.