The unit of currency in China is the Chinese Yuan Renmenbi, abbreviated as CNY or RMB.
Locals will call the Yuan Renmenbi either Yuan, Renmenbi or Kuai, so be aware that all three mean the same thing.
The best way to pay for things in China is with cash. You should always carry at least 100-200 RMB (and at least 500 if you plan to shop). Very few places accept credit cards; those that do usually only accept Chinese cards. Fortunately, all major shopping centers have ATMs, and you typically only have to walk a few blocks to find one if you aren’t at a shopping center.
Even if you do get a bank account in China, you should still always carry the cash you need. Never assume a place will accept your card.