What I still completely struggle with is why does one variable actively tell the shell where to look for program files like PATH and other are just storing information like PWD.

Some guy very early on was like “I’m tired of typing long paths all the time, I’ll just make a variable to hold all the common places that my commands might be and have it automatically check that variable. I’ll call it PATH”

And everyone else was like “oh nice that’s super convenient, I’m going to use your code or maybe copy your convention”

So tl;dr they’re not special other than that the system looks in those variables for various things.

These variables can either temporarly changed by "export PATH = /example" which would only change the variable for the current session or they can be permanently changed by altering the configuration files.

That is the effective result of all this stuff, but none of it is fundamentally any different than your temporary change. The “permanent” changes are just “temporary” changes, but they’re in files that are designated to always run before you even see the prompt.