@techworker1 ,
Omar is absolutely right; the Principled Shader does a lot more than a simple Diffuse Shader.
It has a Specular slider (set to 0.5 by default) and that is related to the Latin word Speculum, meaning mirror and that is related to light (here: environment) reflecting properties of materials (everything reflects some light, apart from black holes) and the Specular Value is directly related to the IOR of the material (unimportant, but the formula is: (((IOR -1)/(IOR+1))^2)/0.08.)
Setting the Specular in the Principled Shader to 0 (corresponding to an IOR=1), would give you a Diffuse (if you don’t use Subsurface, Sheen, Clearcoat or Transmission…) Shader.
