I was thinking about making an OT for this but judging on how other MCU threads are been locked off I'll ask it here.
I was rewatching infinity war last night and something popped into my head that I'd never thought of before: if Thanos and later the Avengers wanted the stones to halve/return half the population why would you need all of them and not just the Aether if it can change reality?
It's not explained anywhere, and for good reason—it's all MacGuffin nonsensical mumbo jumbo.
And that's okay! These stones played individual roles in certain stories, but ultimately they've never been what has really
mattered in the MCU, and outside of their culmination in these last two Avengers movies, they really could have been replaced with any plot contrivance widget or thingamajig.
With that said, I think the reality stone just sort of behaves as an illusion creating thing? Like, we see Thanos use it on Knowhere and then again on his home planet to create visions, but I don't think it actually alters the nature of reality. As soon as the stone is gone, those effects reverse themselves (Mantis and Drax auto-recovering from their weird ribboning and dicing).
But as far as the mechanics, I just assumed the collected stones enhance one another and, essentially, grant wishes? Who the hell knows. Why can you destroy and then revive trillions of beings but not revive those who were killed prior to a snap occurring? Can you accomplish other things besides disappearing people? If you put on the gauntlet and did the shocker or the metal horns or the surfs up gestures would some other marvelous thing happen? Most importantly, why does snapping one's fingers automatically make these things happen? Why don't you have to snap them backwards to undo it? Was there nothing special about the original gauntlet (i.e. it being made by the space blacksmith like Thor's weapons...) since Stark was able to make a functional facsimile out of Iron Man tech?
The questions are endless, but ultimately meaningless. Sometimes the mechanics of magical items and the reasons behind them are best left unanalyzed, and it's okay to let those parts of storytelling go usually (unlike the total illogical and thematically inconsistent character actions and story beats of this season's GoT).