Normal bump mapping is a way of adding high-resolution detail to low-polygon objects. It is especially useful for real-time display devices such as game engines, and it can also be used in rendered scenes and animations.
A normals map is a three-color map, unlike the grayscale maps used for regular bump mapping. The red channel encodes the left-right axis of normal orientation, the green channel encodes the up-down axis of normal orientation, and the blue channel encodes vertical depth.
Remember... the early bird might get the worm, but the second mouse always gets the cheese!