yóuqí shì biérén bāng nǐ diànfù shí, bèizhù ràng duìfāng yīyǎn zhīdào zhè bǐ qián shì shénme, yě fāngbiàn yǐhòu chá

尤其是别人帮你垫付时，备注让对方一眼知道这笔钱是什么，也方便以后查。

Especially when someone pays on your behalf, a note lets them know what the money is for at a glance, and also makes it easy to check later.