Expand folders when dragging over them: If turned on, you can drag files over an unexpanded folder and it will pop open, letting you drop the files into one of its sub-folders.
Collapse after drag (spring-loaded): If the previous option is turned on, this option makes the folders that you've dragged over close again after the drop is complete.
Expansion delay: Configure the time (in milliseconds) that you need to hover the mouse over a folder during drag and drop before it expands.