The x-server has a built in copy/paste function that uses the primary clipboard. Yes, Linux has more than one keyboard - the primary doesn't use the C + V functions.
To copy text to the primary clipboard just highlight the required text with the left mouse button down. Don't close that application yet though. To paste simply press the middle mouse button at the desired point in your document. You can also use the key command of Shift+insert*. Voila!! Copy and paste. This also applies to terminal emulators, so you can copy and paste between terminals and gui apps with ease. The primary clipboard is for text only.
By using the primary keyboard commands you then have two clipboards to play with at once. Primary executes the process described and clipboard (as every one knows it) does C + V. Put the two together and the power of Clipboard is more than doubled!
(* - key command may not work out of some browsers)