Discard vs Charity

[koolkat67]

When can you discard instead of charity?

Example: I've seen when you have to discard a Race card you have to give to Charity (lowest level player) and I've see you can simple discard it.

Is there a difference in what way it is discarded depending on which point you want to get rid of the card...such as a Race card on the table being replaced by another Race card vs removing a Race card from your hand to get down to 5 cards?

And I assume the term "discard" in the game means it goes in the face-up pile.