Butterfly lighting is a glamorous style of portrait lighting best suited for women with long hair. Position the main light with a softbox directly in front of the model's face, but raised up to well above head height, so that it creates a small shadow under the model's nose. The secondary light should be in the position for broad lighting, illuminating the side of the model's face closest to the camera.
Butterfly lighting illuminates the face evenly, and is suitable for people with normal oval faces. It's not really suitable for most men or women with short hair because it tends to highlight the ears, which can look a bit odd in a formal portrait.