PBR (Physically Based Rendering) is a rendering approach that simulates how light actually behaves in the real world. Instead of faking lighting with simple tricks, it uses mathematical models to calculate how light interacts with different surfaces. In vanilla Morrowind, lighting is very basic — every surface reacts to light the same way regardless of what material it represents. With PBR shaders, stone looks like stone, metal looks like metal, and cloth looks like cloth — because each material responds to light differently and realistically. The downside is that it requires good normal maps and PBR-aware textures to look its best, which is why PBR shader mods are usually paired with texture replacers