The third image looks to be greyscale (black n' white), so is it? If so, it's definitely a spec map. That's what it looks like. However, you never know. Some people use things differently with different shaders. You can also use a black and white image for a height/displacement map as well, for instance.
Btw, those images are *not* called "shaders", and the second two are not really textures. Only the color (diffuse) is the actual texture. The other things, like normal maps, are called "materials". The shader is the code that uses all of the materials to create a special effect with the object. They usually are named like this: "filename.fx" or "danielsshader.fx" (fx is a common abbreviation for the word "effect", so it makes sense, right!? :D).
Hope that helps!
