Question

It was the Ghost-type trainer from the E-4, I forget her name, anyway she started talking about the rainbow wing and silver wing.

QUESTION: What are those "wings", where are they, and how do you use them?

Answer 1

The rainbow wing is a key item that summons Ho-Oh in HG,SS,S,G,C in the Bell Tower.
The silver wing is a key item that summons Lugia in HG,SS,G,S,C in the Whirl Islands.

Hope this helped. :D