This is the 3208th most frequent Russian word.
нашему
"To our" or "for our" (dative case of "наш").
Here, 'нашему' is the dative form of the pronoun 'наш' (our), modifying 'другу' (friend) to indicate 'to our friend.'
Мы подарили нашему другу книгу.
We gifted our friend a book.
In this sentence, 'нашему' in the dative case modifies 'соседу' (neighbor), showing the recipient of the help.
Вчера мы помогли нашему соседу с ремонтом.
Yesterday, we helped our neighbor with the repair.
The word 'нашему' modifies 'учителю' (teacher) in the dative case to indicate trust towards our teacher.