The Standard shaderA built-in shader for rendering real-world objects such as stone, wood, glass, plastic and metal. Supports a wide range of shader types and combinations. More info
See in Glossary is a solid example of a 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 using the new PBS System and should be valuable for a range of uses, but you can of course build on this editing the shader and bringing more esoteric materials and workflows to suit your projects.