PBR and BRDF.
Note that there is not the physically based shading, it is rather a container term for methods that use sort of reflectance function to approximate realistic scenes (the term is also used for path traced photorealistic rendering, but that's different). This function, a BRDF (bidirectional reflectance distribution function) describes how light is reflected from a surface. The necessary ingredients, textures for the different channels, can be made manually or via tools like the material maker (which is cool).
Quite a few tutorials and texts with more depth can be found out there, also how to implement it.
