This is the 17541st most frequent Russian word.
трем
The Russian word "трем" typically refers to the dative case of "три" (three) or can relate to "тереть" (to rub) depending on context.
In this sentence, "трем" is the form of the numeral "три" in the dative case, agreeing with "друзьям" to indicate 'to three friends'.
Я подарил каждому из трех друзей книгу.
I gave each of the three friends a book.
Here, "трем" is again the dative case of "три", used with "студентам" to signify 'to three students'.
Мы помогли трем студентам с их обучением.
We helped three students with their studies.
"Трем" in this sentence uses the dative case with "экспертам", denoting 'to three experts'.