Here's a quote from CD Projekt about the partnership:
"Ray tracing allows us to realistically portray how light behaves in a crowded urban environment," said Adam Badowski, Head of Studio, CD PROJEKT RED. "Thanks to this technology, we can add another layer of depth and verticality to the already impressive megacity the game takes place in."
Cyberpunk 2077 was already shaping up to be one of the most demanding PC games in years, but ray tracing is sure to push today's best graphics cards beyond their limits. We're gonna need some next-gen tech to hit ray traced 4K at 60+ fps.
We were able to check out a behind closed doors demo of the new RTX enabled build of Cyberpunk 2077, and while CDPR didn't explicitly state what sorts of ray tracing effects are being used, it did mention the use of global illumination and dynamic lighting effects in the game. There are also plenty of reflective surfaces, but those might be using screen space reflections. Either way, if there's a game that can potentially convince people that it's time to pick up an RTX card, this is the best candidate to date.
Above and below are our first look: Two 4K screenshots of Cyberpunk 2077 with ray tracing in effect. The top one's especially shiny.