Using the
draggable option helper you can decide whether the original element, a clone of it, or some other element (returned by a function) is dragged around.
So the helper option specifies which element should be draggabed around, the value of the option being a string or a function.
The ui.helper property in a draggable event contains the corresponding element, the one being dragged around.
Here's a quick demo showing all three:
http://jsbin.com/ogowe5