What does "ray-traced lighting" do exactly?

[keviny01]

It is such vague term, because ray-tracing is all about lighting, isn't it? So what specific part of lighting does "ray-traced lighting" pertain to? RT shadows and reflections are self-explanatory, but I don't know what RT lighting is. And it is costly to performance too, second to RT reflections. What's more, I took screenshots of RT lighting at ultra (click here) and off (click here), and they don't seem that much different.

 

[tripl3x]

I too have thought it doesn't make much of a difference but turn it off and on while inside a car as a passenger and then the difference is like night and day. Places like the one in your screenshot are easy to light using traditional methods (i.e. baked lighting), but dynamic ones like a moving car are not.

 

[kitanii]

To be fair, both ray-traced shadows and reflections pertain to lighting. They coexist and affect each other as a whole.
RT lighting is just that; Lighting. More specifically it's the illumination of (and between) objects in the world and that's what's affected in this game and implementation. You get a realistic bouncing of lights in areas of a rendered scene where traditional methods can't do the job. Surfaces close to each other realistically gets extra and precise color information that helps the illumination of them. I.E. If You have for example a very vivid red wall across or just close enough to another wall with a surface material that you'd expect too see some of this red color on you get it with great precision.