Files that exist on a computer, but don't appear when listing or exploring, are called hidden files. A hidden file is primarily used to help prevent important data from being accidentally deleted.
Hidden files should not be used to hide confidential information as anyone may view them.
In Microsoft Windows Explorer, a hidden file appears as a ghost or faint icon. For example, in the following image, the hidden file, hidden.txt, has a much lighter icon than the other two icons.
In MS-DOS or the Windows command line, when the dir command is used without any additional switches, you cannot see hidden files. However, using the "attrib" or "dir /ah" command enables you to view any hidden files in the current directory.
It is important to realize that files can also be hidden using a software program or other commands. To view these files, you need access to the program used to lock them. Files may also have permission rights that allow or prevent users from viewing, which may only be given by the administrator (superuser, also known as root).