Copy/Paste and Highlight Usage

There are 3 types of copy/cut and paste methods which exist in X windows, and most modern programs use 2 of them. The 3 cases are:

cut_buffers 0-7

these are obsolete but they still work and are the simplest to use.

highlighting

called primary selection; almost all clipboard programs only use this.

copy and paste

called secondary (or clipboard) selection. Some more modern programs use Ctrl-C/Ctrl-X and Ctrl-V for this (some use other keys or qualifiers, like Shift).