I think a spot of explanation is need, for those new to Linux.
Unlike Windows and MacOS, X11 [1] has two clipboards. One is used when
parts of a document are cut and pasted using the edit-menu and the cut,
copy and paste keys (such as Control-x, Control-c, and Control-v). It
behaves much like the clipboards on Microsoft Windows and MacOS. The
*other* clipboard works quite differently, as it is only used for
copy-and-paste: things are copied to the clipboard when you select them
with the mouse, and they are pasted when you click the middle
mouse-button.
Using the “other” clipboard, you do not need to use the keyboard at all.
You can try it now: open up a text-editor (or start a new email message)
select some text in another program, such as your Web browser, return to
your text-editor and middle-click.
[1] The system that Linux programs normally use to draw graphics to
the screen is called The X11 Windowing System, X11 for short, or
X for even shorter. With X, programs can draw buttons, menus,
text-entry boxes and all the other things that plague our computing
existence. For those of you who are familiar with such things, you
can consider X11 to have a similar task to Aqua on MacOS, and
Avalon on Microsoft Windows.
