butterfly-lighting is when there is a shadow below the models nose almost in the shape of a butterfly. It’s often also called paramount or glamour lighting after it’s constant use in high fashion or glamor shoots. It’s main benefits is that it highlights cheekbones and produces shadows on the neck, making the model look more defined.
Butterfly lighting first appeared when it was used for a portrait of Marlene Dietrich, a German silent film actress who became a Hollywood star in the 1930s, was presented on film in a way that gave this look its name. The technique only grew in popularity from there now commonly being used for glamour shoots as it very flattering for the model.
To achieve this style you start by having the model face forward with the reflector at their waist. Then the light source will be placed above the model and the photographer will stand under the light source with the camera. The light source should be at a higher angle than the models face and been angled down onto their face.
It is a great technique as it doesn’t require great lighting and instead the set up of the lighting is more important than the quality of the light.