Why do we have 3 types of X-selections in LINUX?
Solution 1:
Historical, partly. I'm not sure "secondary" is used for anything at all anymore.
- "clipboard" is what is used by most Ctrl+X/C/V; it is the clipboard you put things into on purpose.
- "primary" is what holds whatever text is currently selected;
it is how X keeps track of what is selected and conveniently may be pasted by middle clicking (or, if you're awesome, clicking right and left buttons at the same time) or by Shift+Insert in
xterm.
Solution 2:
Check here and here.
tl;dr: See Singpolyma's post.