What the heck are “simulation” and “immersion?” Ignoring whatever demented things Ron Edwards of the FORGE tried to redefine them as, here’s what they mean.
simulation – the job of the GM and game world is to simulate an authentic fictional reality. Events unfold according to in-world physics and realistic behavior of the actors in that universe (and not a preconception of story). The game’s rules are meant to simulate that world and not metagame concerns. See A Simulationist Manifesto. Simulation is generally a good first step to enabling immersion.
immersion – the practice of taking on your character’s personality in the game and trying to experience the fictional world through their eyes and make decisions entirely from their viewpoint. Similar in nature to method acting. See Fundamental Elements of Simulationist-Immersive Roleplaying.
I find this to be the most enjoyable form of gaming. It’s rare – most groups role-play very lightly, even when they are generally simulationist. And a lot of recent game design seriously pushes games in other directions – focus on the game rules as a good in and of themselves and/or on story production/enforcement mechanics have even hit D&D in Fourth Edition. People talk about “story immersion” but it’s really a fundamentally different thing that just means “engrossing.”
However, I’ve played in and run some truly deep in character games and they are really awesome experiences. I hope the series really delves into the topic!