This relates to copying files by dragging and dropping in Windows Explorer.
Imagine you have a directory containing a series of files with names like
Document01, Document02, Document03 ... and so on.
Normally, if you select the files in the directory and copy by dragging and dropping, the files will copy in the order in which they were sorted (except that the file you dragged from will copy first). However, if you copy the entire directory, the order in which the files within it are copied seems to be random.
How does Windows decide the order in which it copies these files?