How does a trump card win a trick in skat?

In the card game skat, a trick is won by the highest card of the suit that was led, unless one or more trump cards are played. If any trump cards are played during a trick, the trick is won by the highest-ranking trump card present.1

When a trump suit is named, the four jacks are always the highest-ranking trumps, followed by the ace, 10, king, queen, 9, 8, and 7 of the trump suit. In "grand" bids, only the four jacks serve as trumps. Players are required to follow the suit that was led if they are able; if they cannot follow suit, they may play any card, including a trump card to potentially win the trick.1