Subtractive colors like paint create color by selectively removing some colors from existing light.

Additive colors like backlit or light-emitting displays create color by creating colors of light in various proportions that are then combined.

If you are in a dark room, all paint is black. Until you turn on something with RGB, because then you have some light for it to selectively absorb. However if your RGB is only displaying green light, and you shine it on red paint, it will look exactly the same as black paint (within a certain ballpark of imperfect materials, anyway). Green paint will look green, or white, depending on how your eye adapts, and green and white will be indistinguishable.

That’s the difference between the two color models. Does it rely on other light sources (subtractive), or is it a light source (additive)?

How the brain actually perceives color is really, really wild, so this is all a bit… fluid when you start getting into the weird edge cases, but the general principles of additive=light emitting and subtractive=light absorbing are generally applicable.