I understood that multiple files from at least 2 separate directories are needed to synchronise. But what kind of files are they? Are we just considering all files in general, or just the ones that can be seen with the "dir" command? Also, apart from the files that can be publicly seen with "dir", do we also have to take into account the hidden files, system files, files with no extensions, and/or files located in sub-directories (or just the main outer directory)? Thank you!