Garters hold the hose up. The top of the hose folds over them. If you're using ribbon as a garter, you can have the ends hanging out as flashes. If your garters are elastic, then the flashes hang off of them. You don't have to have any flashes (to me they sometimes seem to be a bit much for casual dress), but you'll still probably need the garters.

I'd never heard the part about identfying whose on your side by their flashes. I'd liketo see a more reliable source before I buy that.