Users accustomed to CTRL+C/V keyboard shortcuts may find themselves reaching for the mouse when using gVim or Vim in a terminal because aforementioned commands do not work by default. So, how to do it?
Short answer would be to select a text in a Visual or Select mode, type
"+y and you have the selected text in a system clipboard. If you need to paste, position your cursor where you want it and type
"+ is just a register, so you can use different yank/put commands with it like
Long answer would be … well, long. Vim uses registers
"* to communicate with other applications. How it does that depends on the operating system Vim runs on.