Then I tell you something that might either blow your mind or be useful in future (or just being fun fact):
On Linux there is the regular copy/paste clipboard, which you already know how it works. But then there is this primary clipboard called primary selection too, that is independent from normal clipboard. Text will be copied to primary selection when you select a text (in example in Firefox). Just by selection the text with the mouse is enough and it will not affect the normal clipboard. Then you can middle click the text from primary clipboard.
Read more here: https://tronche.com/gui/x/icccm/sec-2.html#s-2.6.1