The cleft of venus (also called the pudendal cleft, pudendal fissure, or rima pudendi) is the furrow at the base of the mons pubis where it divides to form the labia majora. The name is a reference to the Roman goddess of love, Venus.
In some female humans, the clitoral hood and labia minora protrude through the cleft of venus, in others they do not. When tight clothes are worn, the fabric of the tight garment may be pulled into the cleft (often because of a central seam, as in jeans), resulting in a situation known as "cameltoe" in slang terms.
The presence of pubic hair can obscure the cleft of Venus. Body art or genital piercings can also affect its visibility. In some women, certain organs like the clitoral hood or the labia minora can protrude through the cleft of Venus thereby restricting its visibility as well. In such instances, labiaplasty surgery is sometimes considered, though this is by no means the norm.
abridged version derived from: http://www.wikipedia.org