https://help.poliigon.com/general-information/what-are-the-different-texture-maps-for
- don't use specular, use gloss / roughness
- don't use diffuse - its there for tutorial purpose
https://support.gametextures.com/article/98-using-our-materials-in-cycles
- set up Cycles PBR in Blender
- material Node type > Principled BSDF
https://www.youtube.com/watch?v=SvTP5_JVsX8
- do normal uv unwrap before doing principled BSDF node
- change image node to 'non-color' except for diffuse
- invert glossy to get rough by adding color invert node 
- for displacement add color2vector node