Where the object "Setting" and the method "text_formatting" (Setting.text_formatting) are ?

I tried to know where the object(constant) "Setting" and the method "text_formatting" ("Setting.text_formatting" in the file "application_helper.rb") come from. I tried to know where they are, but I didn't found anything. I don't understand. The method is undefined in the code. Are they native compiled codes ?

Any ideas ? Thanks in advance.