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.
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
agree with jgzp
its like a female condom sort of