You can create subdirectories by typing mkdir followed by the name you want to call the directory (e.g., mkdir funstuff). You can move into this directory with the cd (Change Directory) command.
By default, people can list filenames but not view the files themselves. In the Private directory, others cannot list files; in the Public and www2 directories, everyone can view the files. Another useful directory is OldFiles, which contains a backup of yesterday's files. All of these subdirectories are in your locker automatically.