What is Fresnel?
Fresnel is an important concept in 3D visualization. It describes the way light reflects off of surfaces. When you render a 3D object, the Fresnel effect determines how shiny or matte the surface will appear.
When light hits a surface, some of it is reflected and some is refracted (bent). The amount of reflection and refraction depends on the angle at which the light hits the surface. If the angle is very shallow, most of the light will be reflected. This is because the waves reflect off of the surface like ripples on a pond.