What part consider outer china?

Outer China generally refers to the regions of China that are located outside the historical heartland, which primarily includes areas like Tibet, Xinjiang, Inner Mongolia, Qinghai, and parts of the northwest. These regions are characterized by diverse ethnic groups, cultures, and geographical features, often encompassing vast deserts and mountains. Unlike Inner China, which is more densely populated and economically developed, Outer China has been less urbanized and faces distinct socio-economic challenges.