The player who wins the bidding chooses which suit is trump for that hand. The trump suit outranks all other suits, so any trump beats any card of a plain suit in a trick. The top bidder normally picks the suit in which they hold the most strength, often a long run of high cards, to help guarantee the tricks they promised. Choosing trumps is a big advantage, which is exactly why players compete in the bidding to earn it. Once trumps are set, everyone plays the whole hand with that suit as the powerful one, so the choice shapes the entire hand.