〜てくれる
Someone does something for memachine translation
FormationThe person doing the favor が + verb て-form + くれる（くださる）
〜てくれる expresses someone doing something for ME (or someone close to me), with a sense of gratitude attached: 友達が手伝ってくれました (my friend helped me). Since the direction of the favor is clearly "toward me", Japanese usually omits 私に — 駅まで送ってくれました by itself already means "took ME to the station".
The subject is the person doing the favor, usually marked with が: 母が作ってくれた料理 (a dish my mother made for me). If the person doing you the favor is a superior, switch to the honorific form 〜てくださる: 先生が教えてくださいました.
Comparison within the same set: 友達が手伝ってくれた (my friend helped me of their own accord) vs 友達に手伝ってもらった (I got / asked my friend to help) — the same event, differing in who is the subject and who took the initiative. Without 〜てくれる, a sentence like 母が弁当を作りました is just a dry report — adding くれました adds gratitude to the sentence.
Examples
友達が宿題を手伝ってくれました。
My friend helped me with my homework.
母が毎朝お弁当を作ってくれます。
My mother makes me a boxed lunch every morning.
田中さんが駅まで送ってくれました。
Tanaka-san took me all the way to the station.