PBR materials became possible with the improvement of RAM in computer hardware, allowing for more complex algorithmic computations. PBR materials have a set of parameters artists can change to accurately mimic real-world surfaces. A PBR material can be moved into any scene, regardless of lighting configurations and it will appear accordingly.
There are ten different types of maps that are used in PBR:
8. Ambient occlusion
10. Emissive colour
It is not uncommon to come across non-PBR materials, however, these are not standardised, so every programme that uses them may vary greatly in approach.