N4
てくれる
To do something for someone (usually you)
おばあちゃんはいつも美味しいご飯を作ってくれる。
Grandma always makes delicious food for me.
Explanation
「〜てくれる」 means 'someone does something for me' (or for my side). The speaker is the one who benefits, and there is a feeling of thanks: 「山田さんは私に傘を貸してくれた」 (Mr. Yamada lent me an umbrella). The receiver 「私に」 is often left out. When the giver is an elder or superior, use 「〜てくださる」.
Mixed up with
The subject is the person who does it, and the receiver takes 「に」: 「山田さんは私に傘を貸してくれた」.
「〜てもらう」 is the mirror image: the subject is me and the giver takes 「に」: 「私は山田さんに傘を貸してもらった」. The meaning is nearly the same, but the subject and particle swap.