> That puts from the "a" register, and you can repeat
  > the action since the register is never overwritten
  > unless you tell it to. You can also use b through
  > to z to store other things.

The '+' register is used to interface with the X11 (or Windows) clipboard. Example:

  "+P   Paste from clipboard
  "+y   Yank to clipboard
  "+gP  Paste from clipboard, move cursor to end of pasted text