The official currency of mainland China is the renminbi - abbreviated to CNY or RMB. Yuan is a unit of renminbi; however Chinese currency is generally known as the ‘yuan’, particularly in countries outside of China.
The name 'renminbi' literally means 'peoples currency' and was first issued in 1948 when the People's Bank of China was established.
It's easily exchanged in Hong Kong and Macau but is not the official currency in those destinations.
The most commonly used bills for Chinese yuan are the 1, 5, 10, 20, 50 and 100 notes.