fog lights question

cobra

Are those come on only when it's really dark or foggy. I turn my lights on and the fog lights switch on during the day and the fog light are not on. I can see the indicator in the dash is illuminated but no fog lights. I tried in the auto mode, still not on. I was wondering If it's because it's not dark enough, please enlighten me. I read the book but they don't say much , I'm in the dark !!