oh, so its a game that gives you choices. Hopefully meaningful ones and not just the illusion of choice.
Well... it's not that it gives you choices, it's how the game's is designed. That design will naturally lead to many choices.
An immersive sim is a game in which, at least ideally, solutions are not pre-programmed. Instead, all the things in the game are pre-programmed to work in certain ways. The player then uses the stuff in the game to come up with a solution.
Say you're in a warehouse with some small tools, a little office, and a lot of crates. You can see a whole in the ceiling up to an attic, but there's no way up to it.
The conventional way to do this would be to code in a way for the player to stack the crates up and use them to get to the attic. If you go back to Infocom games, it may even be looking for you to specifically say "stack crates."
The immersive sim way would be for all the objects to have code that will deal with how they stack up. It would also have code on how to take things apart and how those small tools work. The player could stack boxes up, but the player could also go back to the office and start the stack with a big desk or two. Or the player could even take crates apart and nail together a makeshift ladder to use. Lots and lots of choices, including ones the developers might not even expect!
The conventional way is going to be a lot easier to code, but players that come up with perfectly good solutions are going to be frustrated when they find they don't work. Conventional programmers can cover more and more solutions, but they can't think of everything. With the immersive-sim style, they don't need to. They just set up things in the game to work as realistically as they can, and whatever should work will work.
But how is the player supposed to know which one is going on? About the only way I know is to wait for the game to be out a few months, then search for "developer didn't know you could solve the quest this way" articles, which is a hallmark of immersive sims. Even then, what are you supposed to do with the half-breeds that use some of both styles? <shrug>