This is the 14819th most frequent Russian word.
победителю
"To the winner."
Here, 'победителю' is used in its dative case, indicating the recipient of an action (giving the trophy).
Мы передали кубок победителю конкурса.
We presented the trophy to the winner of the competition.
In this sentence, 'победителю' is again in the dative case, specifying the indirect object (to/for whom applause was directed).
Собравшиеся аплодировали победителю.
The gathered crowd applauded the winner.
The word 'победителю' here denotes the recipient of the congratulations and is in the dative case.