It's helpful to take a few steps back from time to time to reassess where we're each coming from on our knowledge of tech (or anything) to better communicate.
We assume that people know what an OS is, what OS they're running, and how to install an OS.
I've seen it dozens of times, especially on here, where someone describes Linux, convinces the person that they'll like it, and then gets the equivalent of a blank stare when they say 'You just need to download the ISO and install the OS'
My mother is in her 70s, and if you set up her computer to run Linux in the same way that it comes ready to run Windows, she'd be fine after a short readjustment. If you gave her a USB stick with Linux on it, she wouldn't get anywhere because she has no clue what she's supposed to do with it.
She doesn't care about the OS, as long as her browser opens and loads Facebook, letting her keep in touch with her friends.