This shader can be used as a replacement for the texture and bump map shaders, providing extra parameters, and provides a link between the texture and bump shaders (editing one set of values automatically apply to the other shader, something that is useful when using the same image as both a color map and a displacement map).
The extra parameters available let you change the texture without having to edit the image file itself:
You can adjust hue, saturation, and value, the red, green, and blue tint, and reverse the image horizontally or vertically.
You can add noise to the color of the texture, letting you easily create a dirty or faded look.
You can add noise to the UV mapping routine, this will distort the texture by a certain amount, for e.g. special effects or to break up the tiling effect in seamless textures.
Both noises can be tiled to match the tiling of the image itself.
All parameters can be keyframed too, allowing you to e.g. change the tint of a texture over time.