Something quite important to keep in mind is that this is nothing new, there have been raytracers since at least the 70s. However, they were never anywhere near real time. A simple scene with just a few simple objects could take hours to render.
That it is now possible to do with much more complex meshes, more lighting and much higher resolution and also many times per second shows how much faster (and specialised) the hardware has become.
Something quite important to keep in mind is that this is nothing new, there have been raytracers since at least the 70s. However, they were never anywhere near real time. A simple scene with just a few simple objects could take hours to render.
That it is now possible to do with much more complex meshes, more lighting and much higher resolution and also many times per second shows how much faster (and specialised) the hardware has become.