When you have more time to talk about games, than actually play them.
RTX stand for Ray Tracing texel eXtreme, but I think now most gamers know it as the cards everyone wants. Nvidia was the first to introduce affordable real-time ray tracing to the gaming masses.
Ray tracing is a method to mimic how light reflects off of all surfaces. The rays of light will bounce off of different surfaces in different directions. Using ray calculations allows games to show life life reflection, shadows and lighting.
The RTX technology is something that only movie studios could afford to use in CGI scenes where they could afford doing it in real life. It would cost them thousands to produce, but now gamers could see similar results for just hundreds.