Lights can be handled like any other geometry. Their position and/or orientation are determined by the nvsg::Transform node they are child of. There can be any number of lights in a scene, but some traversers might pay attention to only a limited number of them. The nvtraverser::GLTraverser, for example, handles just the first eight lights it encounters.
Currently there are three different types of light sources:
nvsg::DirectedLight A directed light has no position, only direction. It represents a distant light source with parallel rays, such as the sun for example.
nvsg::PointLight A point light has a position in space, but no direction. The light rays emanate from it's position in every direction, such as from a light bulb for example.
nvsg::SpotLight A spot light has both position and direction. The light rays emanate from the position in only a limiting cone around it's direction.