The disks were found in the suva shrine in the Great Temple. Each Kanoka disk was a different color, and each bore the likeness of a Mask of Power. What drew the attention of the Toa Metru was that the masks matched the ones they wore, suggesting that they had always been destined to be Toa.
Masks forged from Toa disks would give the wearer power over the element as though they were a Toa of that element.
Masks forged from Toa disks wouldn't provide the wearer with protection from that element. For instance, a Mask of Fire wouldn't protect the user from burns.