It has a million features I don't use. But some features are really, really nice, like C-q for editing file names (C-x-s to persist changes once done). Rectangle editing is so, so nice to have when renaming multiple files.
They probably mean ‘C-x C-Q’, which toggles a buffer with its read-only state. In this case it lets you edit the contents of the dired buffer (i.e directory or file names) to changing the buffer to wdired-mode, and then ‘C-x C-s’ to save the contents of the buffer, which changes the names and places the buffer back into read-only (dired-mode)