The most common studio set up for lighting is a 3 point set up.
A key light is the main light in use. It is positioned at roughly a 45 degree angle facing the subject, illuminating them from the side. It is good at casting shadows, creating a three-dimensional model effect.
A problem arises, if the subject is beside a dark background, then the key light will cast shadows which make the subject blend into the background.
A solution to this is using an edge light. This brings the subject out of the dark background, and is positioned opposite the key light, still at 45 degrees to the subject. Even if the subject moves or turns, the light will still give them a clear highlighted edge. This combination of key light and edge light is sometimes referred to as a 3/4 backlight set up. When two edge lights are combined, the effect can be dramatic, especially when the key light is dimmed.
A fill light, is a second ‘key light’ that is next to the key light and opposite to the edge light (which is dimmed). I am interested with experimenting with edge lights, to try to create different effects.
A backlight recreates light from above (mimicking midday sunlight), the backlight usually points down.
Something to bear in mind, is that objects bounce light, particularly light objects. This can have an effect on your lighting arrangement, and could be used cleverly as a way of introducing light in unusual ways.
An interesting thing to experiment with is visible, volumetric lighting; where the source of light is visible on camera, this is often used where the air contains light reflecting particles such as dust, snow, rain etc.
These different techniques do not just apply to studio lighting, they can be adopted when filming in settings or even outdoors. I should experiment by getting people to position themselves to conform to these rules of edge lighting etc.