The Fresnel effect is named after the French physicist Augustin-Jean Fresnel who first described it. This effect states that the strength of reflections on a surface is dependent on the viewing angle. The amount of reflection increases on surfaces viewed at a glancing angle.
In blender there are 2 type of nodes represent this effect A. Fresnel Node B. Layer Node (fresnel & facing)
And there is next one I've been recreating from this: https://en.wikipedia.org/wiki/Schlick's_approximation
ARNOLD RENDER uses this type of Fresnel. It is Artist friendly. NOTE that at value = 0 it has much more visible results. I use this constructions for learning purposes and for some of my projects.