Whenever you cut or clip text out of a buffer with a kill command in GNU Emacs, it is stored in a list and you can bring it back with a yank command.
(The use of the word “kill” in Emacs for processes which specifically do not destroy the values of the entities is an unfortunate historical accident. A much more appropriate word would be “clip” since that is what the kill commands do; they clip text out of a buffer and put it into storage from which it can be brought back. I have often been tempted to replace globally all occurrences of “kill” in the Emacs sources with “clip” and all occurrences of “killed” with “clipped”.)