What is Player Agency?

[OldTrees1]

Prepping for a railroad allows you to concentrate on the few encounters you'll have per session, and include lots of detail about those encounters. However, it doesn't require any detail *beyond* those encounters.

Prepping for a sandbox has nothing as detailed as any of the railroad encounters, but requires a greater depth of preparation. You know far more about the things that haven't shown up (yet), so that you have a basis for how the game goes.

Think of it as a Hollywood set of a town (very good looking facade with nothing behind it) versus actually starting a town. The "actual" town won't look nearly as good at first (though it may in the long run), however, it is completely functional even with just a few fairly drab buildings. The Hollywood town set, on the other hand, looks great and like a huge city, but unless you go to the only prepared areas, the whole thing is just backdrop and non-functional.

Very true, albeit orthogonal to what I was talking about.

I was instructing Darth Ultron on why Improv DMing is not "random" and does have the potential for player agency (his ignorant contention was that Improv had no information). Whether it is a railroad, a standard campaign, or a sandbox, improv DMing allows the DM to have access to more information despite having less in the way of written notes. Consider the difference between a written list of the first 20 fibonacci numbers, and a written formula for the fibonacci function.