One important visual cue of objects in the real world has to do with how they become more reflective at grazing angles (illustrated below). This is called the Fresnel effect.
There are two things to note in this example; firstly, these reflections only appear around the edges of the sphere (that’s when its surface is at a grazing angle), and also that they become more visible and sharper as the smoothness of the material goes up.
In the Standard shaderA small script that contains the mathematical calculations and algorithms for calculating the Color of each pixel rendered, based on the lighting input and the Material configuration. More info
See in Glossary there is no direct control over the Fresnel effect. Instead it is indirectly controlled through the smoothness of the material. Smooth surfaces will present a stronger Fresnel, totally rough surfaces will have no Fresnel.