Mandarin Chinese / Guoyu
Mandarin Chinese is called Guoyu or Hanyu. Hanyu is the national language and standard dialect in mainland China. It’s often called Putonghua, Zhongwen or Zhongguohua.
In Hong Kong, Singapore, Taiwan, and other Chinese communities outside of mainland China, Mandarin is often referred to as Guoyu and is spoken alongside local dialects (just as in mainland China). The written characters (Hanzi) always remain the same.