This is true both for the trump suit and for the trump number. If the trumps are red 3 for example, a lead of a red card means that the following players must, if possible, play either a red card, or a 3. If a 3 is lead in another suit, it still counts as a trump, and the following players must again, if they have one, play either a red card or a 3. Where a player cannot follow suit, they need not play a trump if they choose not to. The player who wins the trick leads to the next trick.
Trumps are cards of the trump suit and number trumps.
Number trumps outrank suit trumps. The highest number trump is the number trump of the trump suit. The other number trumps are all of equal velue. If two or more are played in one trick, the first played wins the trick. Trump suit Red, Trump Number 5.