With few things in China being black and white, it’s no wonder there’s more than 1 way to address the Chinese Currency:
“Renminbi” is the official name of the currency introduced by the Communist People’s Republic of China at the time of its foundation in 1949. It means “the people’s currency”.
“Yuan” is the name of a unit of the renminbi currency. Something may cost one yuan or 10 yuan. It would not be correct to say that it cost 10 renminbi.
As it happens, Chinese people rarely talk about renminbi or yuan. The word they use is “kuai”, which literally means “piece”, and is the word used historically for coins made of silver or copper.
Reflecting on my immediate arrival to China and familiarizing myself with the face value of Chinese currency, I’m remembering sales people using both “yuan” and “kuai” when ringing up my total. I wonder if it’s a cultural context that one gets used to using one term or another. Or if there’s a specific situation in which people prefer to use “yuan” over “kuai” or vice versa. Is it really the same as the US colloquial ‘buck’ versus dollar?