How does PBR work?

I saw a video that explained that Monte Carlo Renderers (like Cycles) calculate, say, 64 light paths per pixel and average the result. This is great, but now I want a similarly easy-to-understand description of how real-time PBR shaders work, and everything I find is either about how to use PBR shaders, or it’s a science paper. Does anyone know how they work?

Read this :

Maybe you will understand it better :slight_smile:

Or better video : PBR