By default, you have one light in the scene, attached to your head.
For more realism, you can add multiple lights: suns, light bulbs, candles, flashlights, spotlights, firelight.
Lights can be positioned, oriented, and colored.
Lights do not cast shadows.
There are three types of lights: PointLight, DirectionalLight, and SpotLight.
All lights have an on/off, intensity, ambient effect, and color fields.
PointLight and SpotLight nodes have a location, radius, and attenuation.
DirectionalLight and SpotLight nodes have a direction.
These X3D scenes are adapted directly from the
original VRML 2.0 Sourcebook chapter examples.
Introduction to VRML97 SIGGRAPH98 course notes.