One of the commands available in the Finder on the Macintosh. When applied to a file or folder that has been moved to the Desktop, it returns it to where it came from. When applied to files or folders created on the Desktop, it gives you an error. When applied to Volumes (Hard Disk partitions, floppies, CDs, removable media, &c.), it ejects them without leaving a ghost image on the desktop (once used to copy from one floppy to another, before hard drives were common.) The command has a keyboard shortcut of command(Apple key)-Y.