Council of Elrond

Hi

Does this simply mean any card of your opponents that you have seen through the normal course of play (whether by them playing cards or having to reveal them to you due to a card you play)?

Or is there some narrower definition of what it means? e.g. only for cards that opponent has had to reveal to you due to a card you play.

Thanks

For non-unique cards it is usually impossible to determine that a card on hand that has been revealed to you e.g. in result of Secret News is the same card that has been discarded later but not its copy (does matter if your opponents discards face up; you see a card after action discard has been performed, but not immediately before).
This means that a non-unique card must be visible to you immediately before discarding it to be considered as "card your opponent revealed to you through a mechanism of the game and discarded".