Source : Free On-Line Dictionary of Computing

chmod
     
         ("Change mode") The {Unix} command and {system
        call} to change the access {permissions} of a named file.
        Each file (directory, device, etc.) has nine kinds of access
        which can be allowed or denied.  Different permissions apply
        to the owner of the file, the members of the group the file
        belongs to, and all users.  Each of these classes of user
        (owner, group and other) can have permission to read, write or
        execute the file.  Chmod can also set various other mode bits
        for a file or directory such as the {sticky bit} and the {set
        user id} bit.
     
        Unix {man} page: chmod
     
        (1995-01-31)