Point Lights

Point lights have color and position within a scene, but no single direction. They give off light equally in all directions, as shown in the following illustration.

A light bulb would be a good example of a point light. Point lights are affected by attenuation and range, and illuminate a mesh on a vertex-by-vertex basis. During lighting, Direct3D uses the point light's position in world space and the coordinates of the vertex being lit to derive a vector for the direction of the light, and the distance that the light has traveled. Both of these are used (along with the vertex normal) to calculate the contribution of the light to the illumination of the surface.