It is for deleting files that Windows refuses to allow you to delete while running. I've had to use it to get rid of some persistent spy-ware.
RemoveOnBoot is a shell extension and once installed it puts a new option in the menu that opens when you right-click on the file's icon. If you click on it, it sets the file up for deletion during the next reboot before Windows can lock it.
Thanks for the info, & Merry Christmas.