Lets suppose you have downloaded a file on your unix system which has some name that cannot be used with unix commands. For example, name of the file is "-ROOT- " . Now if you try to copy , delete or rename this file
i.e mv -ROOT- ROOT
you will get error saying something like invalid option -R .
You can access this file using its inode number which can you get by running "ls -i " in the directory that contains the file.