Conceptually I understand that "Ubuntu" itself is basically the kernel and package management stuff, the operating system.
I am still a little confused about the difference between "Gnome" and "Gnome Shell" and also "KDE" and "KDE Plasma".
Kubuntu is defined as: "an official flavour of the Ubuntu operating system which uses the KDE Plasma Desktop"
So, what is the difference between installing Kubuntu and installing Ubuntu (with Gnome) and then installing the "KDE Plasma" desktop instead of Gnome shell?
Does KDE Plasma somehow run better if it is not installed in Gnome?
Best Answer
Let me try to clarify a bit for you.
KDE plasma is about the same as gnome-shell, it is the most recent iteration of KDE.
You can have multiple DE installed, in this case both gnome and kde, without a problem and you can choose which one to log into at the login window .
Right now, KDE can not run on wayland, and is in the process of transitioning to wayland.
gnome-shell can run on either wayland and X11 .
"gnome" is a desktop environment, it includes a bunch of packages other than the window manager such as gedit, nautilus, a number of servies, etc.
gnome-shell is the window manager.
kde is a desktop environment and includes a bunch of packager such as kate, k3b, a number of kde services, etc.
plasma is the window manager (well kwin is the window manager and plasma is the window manager + desktop features such as widgets but generally "plasma" does not generally refer to the additional packages such as kate, k3b, etc).
see What is the difference between a desktop environment and a window manager?
so gnome and kde include a large number of packages of which gnome-shell and kde plasma (kwin) are a part.