A simple answer is people in China.
When we say “speak Chinese”, “Chinese” means Standard Chinese, Mandarin, Putonghua (普通话). Besides Mandarin, people speak some dialects in different parts of China. For example, most people living in Guangdong(Canton) province speaks Cantonese. But not all people living in Canton speaks Cantonese. Teochew and Taishanese are also important dialects in Canton. You may hear them in Chinatown all over the world. Don't panic if you have learnt Chinese for a long time and find that you can't understand what local people are saying.