Mandarin is a group of Chinese dialects that are considered the official language in many Chinese-speaking communities. The Beijing dialect is considered as standard pronunciation of Mandarin. Thus, when people say the "Chinese language", they implicitly refer to Mandarin.
Mandarin is one of the most spoken languages in the world with over 837 millions of native speakers.
It is a group of dialects, mostly from the north to the south-west China. Its standard pronunciation is the dialect of Beijing. It is also known in China as 普通话 putonghua or 'the standard language'.
Taiwan refers to it as 國語 guoyu, 'the national language', whereas in Southeast Asian Chinese communities such as those in Singapore and Malaysia it is common to hear 华语 huayu or 'the language of the Chinese (华人 huaren)'.