Yes, we've all heard endless jokes about how men have two heads and women have two pairs of lips. The truth is, however, that women have three sets of lips; one up top and two down below.
Although they are commonly referred to as the inner and outer lips, the proper terms for these wonderful tissues of flesh are labia major and labia minor.
What are the labia?
The labia major (the outer lips) cover the vulva (the entire vagina) and protect it from the ugly bacteria of the outside world. Another factoid that might blow you away is that her vagina is much, much cleaner than your mouth. The lips extend from the mons pubis (the area over the pubic bone) to the perineum (the spot between where the lips end and the anus begins).
The labia minor (the inner lips) enclose the urethra and the vagina. During sexual arousal -- which we're hoping will occur often -- the inner lips become engorged with blood.