Actually there's at least five ways of copying and pasting text it in Linux.
1. Rudge's Unix way: highlight and middle click (or highlight and click both buttons).
2. The old Windows way: Ctrl+Insert and Shift+Insert.
3. The Mac-inspired Windows way: Ctrl+c and Ctrl+v.
4. The newbie way: using the menus.
5. Using a program like Klipper in combination with any of the above.
2, 3 and 4 are sometimes useful if you want to replace text. If you want to change the word "foo" to the word "bar", you can't just higlight "bar", and then highlight "foo" and middleclick, because highlighting "foo" would change the copied text to "foo" and the middle click would have no visible effect. But you could highlicht "bar", hit Ctrl+c, highlight "foo", and hit Ctrl+v.