This is the 87th most frequent Russian word.
ему
"To him" or "for him."
In this sentence, 'ему' acts as an indirect object and means 'to him'.
Я дал ему книгу.
I gave him a book.
Here, 'ему' denotes possession or association, translating to 'for him'.
Эта куртка ему к лицу.
This jacket suits him.
In this case, 'ему' expresses a certain state for 'him', functioning as a dative experiencing subject.