Does 'discard' mean you can discard cards from the field, or only from your hand?

Ruling: Discard means moving a card from your hand to the trash. Cards on the field cannot be discarded; they can only be killed to go to the trash.

Nuances:

• Discarding moves a card from hand directly to trash without activating or executing its normal rules text
• This is general TCG knowledge that applies across most trading card games