Is fluoride good for you or bad for you?

I've always been told by dentists and orthodontists that you have to use fluoride in your daily oral hygiene routine or it cause sever damage to your teeth (tooth decay, staining, etc.)

However, fluoride stains your teeth, brown spots or white spots, and I've heard it can even weaken bone structure and the tissue that hold your teeth in place. (My mother also told me not to trust that fluoride is good because thats just what the goverment tells the dentists and..teeth people, and that it poisons you or something- I don't really remember)

I'm super paranoid of any damage to my teeth, and this question freaks me out. Any answers are appreciated, thanks!​