How (and where) does Unity save the modified parameters of a prefab's instance?

I am using a prefab (say a piece of environment, like a mesh) with some specific behaviour (it has a script as a component attached to it).

Said script contains several variables, preset by default, and many of them accessible in the Editor's inspector, for rapid tweaking. This way, the prefab is sufficiently modular. Now, I produce ten instances of that prefab in a scene by dragging the prefab in the 3D view. Then, I modify some of the values of these instances in the Inspector (tick some cases, change public vars like floats or ints). Not all instances are modified the same way, for the sake of variety. All overriden parameters now appear bolded.

I save the scene. Build for mobile, etc. During runtime, at the beginning, the game will produce a pool of those instances and will manage to retrieve then place each instance as I had put and saved them in the project's scene, with the specific modified parameters. So far so good.

Unity uses a system so as to know, when loading (activating) each instance individually, how to modify them according to my earlier choices.

Now, I'm unsure how nor where Unity saves the data specifically relevant to these overriding parameters. Is it saved in a single global file that can't be reached in the Editor? Is that file attached to the project as a whole, or is it divided into several files, one per scene or per prefab specifically? Or does Unity even produce more of them, one for each instance? What is the way to access and read this or these file(s)?

TL;DR: how does Unity store the list of all instances' modified parameters that will be read later on in game when recreating my scene?

Thx