Hi, welcome to the forum!
It works basically like Windows Explorer. The default is move on same drive, copy to different drive. You can hold Ctrl or Shift depending on which one you want, and it will switch move to copy or copy to move (this should be shown in the hover text when you're over the folder)
Steven, if you happen to catch this, is that correct that you have to use a different key to change move to copy (Ctrl) than copy to move (Shift). I would have figured the same key could do both.