Pretty sure most of you already know this but for those who don’t: you have two clipboards in Linux. One is the traditional clipboard where you copy with control c and paste with control v. The other one is when you highlight text and use the mouse middle click to paste text.
More details here.
Wait till you figure out that deleting stuff in the terminal (eg c-w) is saved in a separate pastebuffer too (c-y for yank, so yankbuffer?)