This is the 2182nd most frequent Polish word.
prezydentowi
"Prezydentowi" means "to the president" (dative case in Polish).
The word 'prezydentowi' is in the dative case, used here as the indirect object of the verb 'podziękowaliśmy' (we thanked).
Podziękowaliśmy prezydentowi za jego wsparcie.
We thanked the president for his support.
'Prezydentowi' indicates the dative case to mark the recipient of the medal in this passive-voice structure.
Prezydentowi miasta wręczono medal.
The city's president was awarded a medal.
Here, 'prezydentowi' is again in the dative case as the indirect object of the verb 'pomagam' (I am helping).