Simple Lambertian reflectance model. Outputs a simple color (RGB).
The opacity of the material expressed as a color value.
Connect a normal map here (usually exported from Mudbox or ZBrush).
Normal mapping works by replacing the interpolated surface normal by the one evaluated from an RGB texture, where each channel (Red, Green, Blue) corresponds to the X, Y and Z coordinates of the surface normal. It can be faster than bump mapping since bump mapping requires evaluating the shader underneath at least three times.