What is it? And how do you use it/
a dental dam is a thin sheet of latex it can be used both in dentistry (when putting fillings into teeth) and for oral sex it can be used during oral sex (put it over the head of the penis or more commonly, over the vagina) to protect against getting stds or transmitting any bodily fluids and also for rimming (when someone licks your anus) so you dont get any poo or other fluids on or in you
its used for preforming oral sex on a female... its like a piece of thin plastic-like material that goes on the outer part of the vagina before the partner preforms oral sex.
agree with jgzp its like a female condom sort of