In principle I know what GNOME shell is. Can I delete multiple instances of it?

Preface

This question regards Gnome [1]. Before proceeding any further, the reader should understand what Gnome is. One answer to this question, which is posted below by Henning Kockerbeck, suggest that I should look at a website to understand what Gnome is. Let me be clear, after getting 5 down votes, I went to Gnome.org. In my humble opinion, there is nothing there that spells out in simple terms what Gnome actually is. My best guess is that Gnome is not one thing at all, but rather several. Gnome appears to be a foundation; an amalgam of technologies [2] with which to use the Linux operating system; and a shell called GNOME shell. The latter is probably what is referred to by the applications gnome-3-38-2004 and gnome-42-2204 (see below).

Further, as suggested below, a more useful account can be obtained by Wikipedia [3]. There it states that,

GNOME Shell is the graphical shell of the GNOME desktop environment.... It provides basic functions like launching applications, switching between windows and is also a widget engine.

This quote is important to the question at hand because it appears---indeed---that this question is better rewritten as In principle I know what GNOME shell is; can I delete multiple instances of it?

Context

In a previous question [10], I asked about removing var and usr directories. The motivation was because I kept getting messages about low disk space in my root. In answer, Merilyn Ne referenced [20], which offers 10 Ways to Clean up Your Ubuntu System to Free up Disk Space. Item 2 of 10 on the list is to removed remove unused applications. When I look at the list of installed applications, I do not know what some of them are and if I need them, or not.

Questions

(1) Can gnome be safely removed?

(2) If there are more than two gnome installed (e.g., gnome-3-38-2004 [362 MB] and gnome-42-2204 [430 MB]) can one, or both, be safely removed?

References

[1] https://www.gnome.org/

[2] https://www.gnome.org/technologies/

[3] https://en.wikipedia.org/wiki/GNOME_Shell

[10] should I delete var or usr directories

[20] https://fostips.com/clean-up-ubuntu-free-disk-space/

GNOME is a desktop environment (DE) for Linux. Ubuntu uses GNOME as its default graphical user interface (GUI), but there are other GUIs and DEs you can use alternatively, from KDEs plasma desktop to more classical DEs like Cinnamon or explicitely small GUIs like LXDE or Xfce.

Basically, GNOME and the others I mentioned are responsible for giving you a mouse pointer, windows, buttons, menus, icons, the whole graphic user interface. If you're using another DE than GNOME (or don't want a graphical interface at all), then you can theoretically remove GNOME. But if you're so low on ressources, maybe the "main flavor" of Ubuntu isn't right for you machine, and you might want to look at something like Lubuntu or Xubuntu.

And as a general remark: Ubuntu comes with several thousand software packages you can install, plus the packages from third-party repositories. Please don't ask a question for each of those whether or not you can remove it ;) In most cases, the project homepage of the software in question gives you an idea of what it is and what it does, sometimes even Wikipedia (as we've seen above). If there's still something you don't understand after you tried to find it out for yourself, by all means please ask. But so far, it feels at least to me like you're expecting to be spoon-feed.