This is the 194th most frequent Japanese word.
くれる
To give (used when someone gives something to the speaker or their in-group).
くれる is used to indicate that the subject (友達 - friend) is giving something (プレゼント - present) to the speaker, highlighting the relationship and the direction of giving.
友達がプレゼントをくれた。
My friend gave me a present.
くれる here expresses appreciation for something beneficial done for the speaker by another person (in this case, 'teaching').
あなたが教えてくれて、本当に助かりました。
You teaching me was truly helpful.
くれる is employed to show that the speaker's older brother (兄) performed the action of lending the book (本) to the speaker, emphasizing the personal receipt of this gesture.