Ragging is one of the more basic faux to learn. They’re often used as a base layer for more complicated finishes such as faux marble. The folds in the rag create a soft irregular pattern, similar to parchment.
Ragging was also used on this decorative plaster. A glaze was applied to the bison, then removed with a rag. The deeper crevices are then stippled to ensure the glaze isn’t applied too heavily. This technique emphasizes the design in the decorative plaster.
By contrast, sponged finishes typically leave a more speckled look. You can see them here.