The word くれる when used in combination with another verb expresses that a favor was done. くれる refers to any action done by another person for the speaker. For example: 彼女はケーキを作ってくれました。 She baked a cake for me. In your example, the sentiment is quite similar: ～分かってくれます。　understand(s) (for) me. I'll create a sentence to give it more context and so that it's easier to see what I mean. 先生は私の長い説明の後でとうとう分かってくれました。 My teacher finally understood (for) me after my long explanation. This kind of expression in English sounds very strange when using the verb "understand (the preposition "for" would never be used in this context in English)," but this kind of expression in Japanese shows an aspect of Japanese culture. It is a way of showing respect to someone and also that you are appreciative of what was done for you. I must say, too, that my explanation is entirely based off of my own experience in the language and how I interpret these sorts of situations as I come across them. I am not 100% certain that I am correct in my thinking about why くれる is used here, but that is the best way I can think of to explain it. A native speaker will also be able to confirm the accuracy of my explanation. I hope this helps. If you have further questions, please let me know.

分かってくれます: you would be understood by ... 彼はあなたのことを分かってくれます : He will understand you.

Just wanna say, if you really want to level up your Japanese, then you shouldn't waste too much of your time on the music because when it comes to Japanese, music is the worst kind of medium to learn the language, the only thing you gain from translating the lyrics is some vocabulary, grammar. In term of speaking/listening, it doesn't help at all, because in real life, no Japanese pronounces words like they do when they sing. Well, but it's up you to decide, just wanna warn you as a fellow learner :).