Despite the similarity in their common names, giant panda and red panda are not related to each other. They belong to totally different families with no connection whatsoever. However, it's also worth noting that we usually refer to giant panda―the bear native to China―when we say panda.
Also referred to as giant panda bears, they are endemic to the central-western and southwestern regions of China. These bears are typically characterized by the large, black patches over their eyes, ears, and body. Though they are classified as carnivores, 99 percent of their diet consists of bamboo grass. Their habitat spans the mountain provinces of central China. In these mountains, they are found at elevations of around 3,000 meters. In winter though, they descend to an altitude of around 800 meters. The natural habitat of giant pandas is typically characterized by bamboos on which they feed.
While a large part of the giant panda population is concentrated to the Sichuan province in southwestern China, provinces such as Shaanxi and Gansu in northwestern China also have a significant share to their credit. Basically, there are two subspecies of giant panda: the Ailuropoda melanoleuca and Ailuropoda melanoleuca qinlingensis. While the former is typically black and white in color, the latter is brown and white. Of the two, the Ailuropoda melanoleuca qinlingensis, a.k.a. the Qinling panda, is endemic to the Qinling Mountains in Shaanxi province.
Neither is the species related to giant panda, nor does it belong to the bear family. Basically, Red pandas are the only members of the Ailurus family of mammals. They are typically characterized by their reddish-brown fur and bushy tails. They are native to the temperate forests of the Himalayan mountain range in Asia, wherein they are most often found at elevations of 2,200 - 4,800 meters. There exist two subspecies of red panda: the Western red panda and Styan's red panda. The Styan's species is relatively larger and sports a dark coat. The Brahmaputra river acts as a geographical border between the habitat of these two subspecies. Their highly adaptable nature ensures that they are found in captivity in various parts of the world.
The Himalayan mountain range, which is home to red pandas, is a long chain of mountains in central Asia. Their population is largely restricted to Nepal and China. Other Asian countries such as India, Myanmar, and Bhutan are also home to this species, but their concentration in these countries is relatively low. The Western red panda is found in Nepal and India, while the Styan's red panda is found in southern China and northern Myanmar.
That covered the natural habitat as well as geographical range of giant panda and red panda species. While the red panda has been declared vulnerable by the International Union for Conservation of Nature (IUCN), giant panda is considered endangered. Though the two are not related to each other, various factors which have been contributing to the decline in their numbers are by far the same. The driving factor being habitat destruction as a result of large-scale clearance of land for farming and logging. As in the case of several other species, even these pandas are falling prey to human interference in their natural habitat.