Ray tracing has long been gaming's holy grail. A method of creating hyper-realistic lighting and graphics, for years ray tracing has been promised as the technology that will take games the next step closer to total realism. Ray tracing has perennially been just on the horizon, but at GDC 2018, but NVIDIA and Microsoft both showed off technology that could make ray tracing a reality.
Typical graphics technology, struggle with how light works. Most games used rasterization, which draws a frame almost the same way someone paints a picture, one bit at a time, and with a lot of approximation. Ray tracing hews closer to how light works in the real world, by modelling millions of beams of light, and calculating how they'd bounce around a scene.