Below voluminously explained the context of the question stated in the question title:
I have started to use Emacs very intensively some days ago and are still bumping into doing things the wrong way. The main reason for the confusion is in my eyes the weird and misleading wording describing the components of the Emacs GUI-interface which differs from the common-sense understanding used by for example the Emacs underlying GTK.
A best example of what I am talking about are the words "WINDOW", "FRAME" and "TAB":
I have in between found out that what in other GUI-applications/interfaces and desktops is called 'window' is in Emacs described as a 'frame' right?
So if I want a new window (i.e another Emacs instance running in its own GUI with a title bar, menu, toolbar, minimize/maximize/close icons) and create one in Emacs using the Menu item "New Window Below" or "New Window on Right", I will get what in all to me known other GUI-applications is called a "multiline text input/output" element/widget embedded in a frame (called in Emacs a 'tab') shown in a window. In other words if I want actually a new 'window' in the common-sense of this word, I have to click in the 'File' menu: 'New Frame'.
Another possible cause of confusion are the concepts behind combinations of the words "TAB", "BUFFER" and "WINDOW".
The Emacs concept of a 'buffer' covers the underlying textual data which can not only be shown and/or edited in one or more windows, but also can stay hidden/invisible in the background. An Emacs-buffer lives an own life not depending on being shown anywhere. What have initially confused me is that after I have killed an 'Emacs buffer' (in order to close a tab) this affected all other tabs showing this buffer in their 'Emacs windows'.
So if I create in the Emacs GUI a new 'Emacs tab' I actually create in terms of the common-sense language a 'frame' which can hold multiple 'multiline text input/output' elements/widgets called 'Emacs windows' which then can visualize content of one of the available 'Emacs buffers'.
If the reason for this way of naming the GUI elements is of historical nature, why does Emacs evolving to modern new versions still stick to the old naming conventions instead of breaking with them and adapt to the changed reality?