13.4 Killing on Graphical Terminals
On multi-window terminals, the most recent kill done in Emacs is
also the primary selection, if it is more recent than any selection
you made in another program. This means that the paste commands of
other applications with separate windows copy the text that you killed
in Emacs. In addition, Emacs yank commands treat other applications'
selections as part of the kill ring, so you can yank them into Emacs.
Many window systems follow the convention that insertion while text
is selected deletes the selected text. You can make Emacs behave this
way by enabling Delete Selection mode, with M-x
delete-selection-mode, or using Custom. Another effect of this mode
is that <DEL>, C-d and some other keys, when a selection
exists, will kill the whole selection. It also enables Transient Mark
mode (see Transient Mark).