The indent just above the upper lip is known as the philtrum. This feature serves no practical purpose but is a vestigial reminder of the development that takes place in the womb.
When the fetus is developing, the two sides of the face grow independently, meeting in the center. When they do not meet correctly, a cleft palate is the result, occurring approximately once for every 750 births. In ancient Rome, people thought the philtrum was erotic, referring to the bend in the lip as "Cupid's Bow." The word philtrum even comes from the Greek word for "love potion."