first of all there is the wii #. to get this you have to go to the message board and then to the adress book.the front cover of the adress book will have your wii#. you can exchange these #s with a friend so that it will give you the ability to mail them things.
EDIT: the numbers they give you are really wierd. every friend code and wii code i have ever got from nintendo has 666 together.