What we are witnessing, so, are Nvidia's first experiments of games featuring hybrid rendering: While games are still rendered with the conventional methods (rasterization), Ray Tracing is getting used just to calculate some graphics elements, like shadows (Shadows of the Tomb Raider), reflections (Battlefield V) or global illumination (Metro Exodus). Path Tracing work in a similar way, but, once rays reach an intersection point, they act more in a life-like way: They keep bouncing through objects getting more precise informations till they reach light sources. Ray Tracing works more or less in the opposite way: Rays are sent starting from the digital camera and, once they meet an intersection point, they send new rays to every light sources. These rays travel till they reach an object, where they'll bounce from countless times to any other object in the ambient bringing with them informations like color or light, until they eventually reach our eyes. In real life any light source emits a tons of rays.
Ray Tracing is a rendering technique known for years in Computer Graphics that aims to produce physically correct 3D scenes.
