It’s important because Linux gives a user lots of options, unlike Windows and macOS, which are essentially one integrated system with just applications that get installed.
This is not to say Linux is “complicated” because for any distro chosen, it downloads and installs as a “single system” as a distro is basically packaged from a bunch of choices made by the distro provider. This is why you’ll sometimes see Ubuntu GNOME and Ubuntu KDE as complete downloadable distros.
But Linux is also not fixed by the distro you install. You can for example change the desktop environment, and you can switch between two or more desktop environments.
This is one reason why understanding some key concepts can help clarify things for users. Another good reason is if you do need some help with diagnosing a problem, it does help that discussion if the concepts mentioned are understood (everyone on the same page).
But also do not let this put anyone off, as many new users download and install say Linux Mint Cinnamon, and are perfectly happy not knowing what parts there are to the system.
The linked article will unpack the concepts of a Distribution, a Desktop environment, a Package manager, the Command line, and your Home directory.
See https://www.zdnet.com/article/5-essential-linux-terms-every-new-user-needs-to-know/