[Chris Holland] “What does “GI” stand for ? “
Global Illumination, also called Radiosity, takes into account light bouncing off objects like in the real world, not just straight ‘light to object’ illumination, very slow needs a speedy computer and it still feels slow – but can be gorgeous… it also can use the Luminance in textures as light sources, a scene can be lit with no lights at all – you need the Advanced Render Module for this.
[Chris Holland] “in general how do they get the whole “world” to be lit like that without falling into complete darkness ? “
Radiosity can be faked, lights under the floor/behind walls with shadows turned off that imitate light bouncing off the floors/walls onto objects. There are also Ambient lights (any light in C4D can do this it’s just in the settings) that light everything, kind of a bad choice since it lightens the shadow areas as well.
Light domes are another choice, a big sphere with lights at all it’s points, all the lights set to a low value. Light comes from everywhere so it’s similar in some ways to GI in it’s look if you are lighting objects like the robots and not a room – check out Lumen Lite (free plugin) here https://www.biomekk.com/index.php?page=1&cat=107&itm=2
Overall it’s a huge subject that takes some learning. There are lots of books on the subject and probably web sources I am unaware of.