It refers to a card that contains the specified text or icon in its name, traits, effects, inherited effects, (Rule), digivolution requirements, DNA digivolution, DigiXros requirements, burst digivolve, App Fusion, Link, or Assembly requirements. For example, a card with [Knightmon] in its text would include cards with the name [DarkKnightmon] and cards with the text [Knightmon] in their effects.