Lately I have been comparing the creation of materials/shaders in the properties panel the creating the same material in the compositor and it is interesting. I think I will put together a video showing what is happening in each as you build your material in one and then the other. Working on the material in the properties panel  from creation is not nearly as intuitive as in the compositor as you will see however once you see how your actions in the material panel affect how and where nodes show up in the compositor things start clicking into place.

Going to end this now as I am haveing serious network problems here at home.