This is the 8737th most frequent Polish word.
robertowi
"Robertowi" means "to Robert" (dative form of the name Robert in Polish).
Here, the word 'Robertowi' is the dative case of the proper noun 'Robert', used to indicate the indirect object of the verb 'podarowałem', showing to whom the action is directed.
Podarowałem prezent Robertowi.
I gave a gift to Robert.
In this sentence, 'Robertowi' again appears in the dative case, here indicating the object of trust within the context of the verb 'ufałem'.
Ufałem Robertowi przez wiele lat.
I trusted Robert for many years.
Here, 'Robertowi' is the dative case and acts as the recipient of the help given, detailing the person benefitting from the verb ‘pomogłem’.