Apple Fitness+ is a health value-added service launched by Apple. Officially released at the end of 2020. Fitness+ is an extension of the original "fitness" (called fitness in China) application, which projects the movement records of watches on (relatively) big screens such as iPhone, iPad and Apple TV. Users can concentrate on following the exercise tutorial on the screen, and there is no need to often raise their wrists to look at data such as heart rate and duration.
However, due to the inability of users in Chinese mainland to open Apple One service, it is not related to fitness+service at present. I don't know if Apple will consider launching an independent fitness+service in Chinese mainland.