It's just a travel document it's very easy to get one. Just like getting a tourist visa anywhere else but you have to check in a bit more often. This is also not exclusive to Xinjiang or Tibet.
It is exclusive to Tibet compared to the rest of China, where foreigners can travel freely with just a visa. In Tibet AR (but not Tibetan autonomous counties in other provinces) foreigners need to travel with a group and special permits.
Chinese citizens travel freely all over except HK and Macau as far as I know, they need permits to go there.
It's just a travel document it's very easy to get one. Just like getting a tourist visa anywhere else but you have to check in a bit more often. This is also not exclusive to Xinjiang or Tibet.
It is exclusive to Tibet compared to the rest of China, where foreigners can travel freely with just a visa. In Tibet AR (but not Tibetan autonomous counties in other provinces) foreigners need to travel with a group and special permits.
Chinese citizens travel freely all over except HK and Macau as far as I know, they need permits to go there.