DirectX Lighting vs. Real World Lighting
In DirectX you can create different types of lights that will make your scene seem more realistic. But the lighting model that DirectX uses is only an approximation of light in the real world. In the real world, light is emitted from a source like a light bulb or torch and travels in a straight line until it fades out or enters your eye. As light travels, it can hit objects and be reflected in a different direction. When it is reflected, the object may absorb some of the light. In fact, light can be reflected hundreds, thousands or even millions of times before it fades out or reaches your eye. Light is reflected differently by each object depending on the material that it is made of. Shiny materials reflect more of the light than non-shiny materials. The amount of calculations to model this in virtual 3D space is too large for real-time rendering. So DirectX approximates lighting.