I’m not sure what rendering does. Also how to get a mindblowing lighting.
Rendering is the process where it takes all of the elements together and creates the final image.
It can involve things that are done ahead of time–like setting up materials, and baking lighting–to things that happen in real-time while you play the game, like post process effects that create bloom/lens flares/depth of field/motion blur, etc.
Explaining is a bit too much to ask I think.
Try wikipedia as your starting point: 3D rendering - Wikipedia
What Darthviper107 said. “Mindblowing lighting” is a result of carefully placed lights, good textures, and a lot of patience. Check out the starter content levels to get a good idea of what goes into a level. You would probably get a lot of use out of breaking down some of the different levels to see how they are put together.