Philtrum is the region located between the nose and upper lips (starting from the bottom of the columella to the upper margin of the procheilon). Philtrum is also often used to describe the middle depression on the upper lips, and its length plays a vital role in determining the overall shape of the upper lips. So the purpose of the philtrum reduction is to create more balanced and youthful appearance. 

Philtrum refers to a slight indentation on the inside of the philtrum. If the philtrum is present, the mid-lower facial area appears three-dimensional, but if the philtrum is congenitally or acquiredly blurred, it may appear less three-dimensional and give an unnatural feel. Philtrum shape creation is a type of philtrum plastic surgery that involves transplanting fat into the philtrum column and excising some of the tissue in the area corresponding to the philtrum to make the blurry philtrum clearer, creating a three-dimensional effect and natural philtrum shape.