Portrait photography, or portraiture, is a type of photography aimed toward capturing the personality of a person or group of people by using effective lighting, backdrops, and poses. A portrait photograph may be artistic or clinical. Frequently, portraits are commissioned for special occasions, such as weddings, school events, or commercial purposes. Portraits can serve many purposes, ranging from usage on a personal web site to display in the lobby of a business.
Three-point lighting is one of the most common lighting setups. It is traditionally used in a studio, but photographers may use it on-location in combination with ambient light. This setup uses three lights, the key light, fill light, and back light, to fully bring out details and the three-dimensionality of the subject’s features.
The key light, also known as the main light, is placed either to the left, right, or above the subject’s face, typically 30 to 60 degrees from the camera. The purpose of the key light is to give shape to and emphasize particular features of the subject. The distance of the key light from the camera controls the falloff of the light and profoundness of shadows.
The fill light, also known as the secondary main light, is typically placed opposite the key light. For example, if the key light is placed 30 degrees camera-left, the fill light will be placed 30 degrees camera-right. The purpose of a fill light is to combat strong shadows created by the main light. Intensity of the fill light may be equal to the main light to eliminate shadows completely, or less intense to simply lessen shadows. Sometimes, the purpose of a fill light may be served by a reflector rather than an actual light. (Source Wikipedia).