The Bartholin's glands lubricate the vaginal orifice and the surface of the vulva. They secrete mucus upon sexual excitement to reduce friction on the genitals.
Bartholin's glands are located in a pair slightly below the entrance to the vagina, closer to the anus than to the clitoris. They are located on both sides of the entrance to the vagina. The amount of fluid they secrete is relatively minor. There are glands deeper within the vagina that provide the majority of lubrication when the orifice is being penetrated. However, the fluid provided by the Bartholin's glands does coat the outer genitals and makes contact with the vulva more comfortable. Since most forms of sexual penetration involve some contact with the vulva, not just the inner structure of the vagina, they serve an important role.