Three Point Lighting
Key Light
The Key light, also known as the main light, is usually the strongest and has the most influence on the look of the scene because it is the brightest light. It is placed to one side of the camera/subject so that one side of the subject is well lit and the other side has some shadow. This gives it more natural looking lighting in the scene.
Fill Light
The Fill light is the secondary light which is placed on the opposite side of the key light. It is used to fill the shadows created by the key light. The fill is softer and lighter than the key light. To achieve this, you could move the light further away to decrease the size of the shadows projected onto the background and to make your shot much more clean.
Back Light
The back light is placed behind the subject so it lights the subject up from behind. Rather than providing direct lighting, the purpose of the back light is to provide definition and highlights around the subject, making an outline around the subject. This helps separate the subject from the background and provide a three-dimensional look. A fourth light can be used placed diagonally to the key. This can make the background lighter and brighter, evicting any left over shadows on the background.
Three point lighting is used as it illuminates the person in shot, making them stand out from the background and much clearer to the audience.
References
"Three Point Lighting". Mediacollege.com. N.p., 2017. Web. 24 Mar. 2017.
